Here are the details about gear modifications. I'm putting them here because it's hard to fit them inside in-game tooltips. Any mods not listed here are most likely projectile mods which add additional projectiles to an attack.

General:

• Shred - Attacks deal an additional percentage of the target's health as damage.
  
• Shield - Attacks generate shields.
  
• Refund - Attacks generate energy.
  
• Heal - Attacks generate health.
  
• Rage - Attacks increase the damage of the next attack.
  
• Block - Attacks generate block charges that increase protection but are consumed when damaged.
  
• Armor - Attacks increase protection.
  
• Regen - Attacks generate health over time.
  
• Anti-g - Attacks cause targets to float.
  
• Glue - Attacks slow targets.
  
• Thorns - Holder of gear receives the "thorns" status effect.
  
• Energize - Attacks generate energy over time.
  
• Perfect - Attacks deal more damage at full health.
  
• Cursed - Deal and take more damage.
  
• Stun - Attacks stun targets.
  
• Ground - Attacks ground targets.
  
• Nano - Attacks confuse targets.
  
• Venom - Attacks apply a damage-over-time effect that deals increasing damage over time.
  
• Deathbomb - Targets explode on death.
  
• Glow - Attacks make targets glow.
  
• Bleed - Attacks cause targets to receive reduced healing.
  
• Smash - Attacks cause targets to receive more damage.
  
• Mark - Attacks mark targets.
  
• Spite - Being damaged increases attack damage.
  
• Frantic - Being low on health increases attack damage.
  
• Weaken - Attacks reduce the damage of targets.
  
• Rush - Attacks increase movement speed.
  
• Hurtful - Slightly increased damage.
  
• Titan - Greatly increased knockback but decreased damage.
  
• Strong - Increased knockback.
  
• Feeble - Decreased knockback but increased damage.
  
• Rapid - Greatly increased attack speed.
  
• Slow - Decreased attack speed.
  
• Light - Increased attack speed.
  
• Heavy - Greatly decreased attack speed.

Guns:

• Pull - Attacks pull enemies towards you.
  
• Bounce - Projectiles bounce off terrain.
  
• Pierce - Projectiles pierce.
  
• Crit - Projectiles have a chance to deal more damage.
  
• Fast - Projectiles travel faster.
  
• Snail - Projectiles travel slower.
  
• Explode - Projectiles explode.
  
• Ricochet - Projectiles have a chance to bounce off targets.
  
• Delay - Projectiles start slow and accelerate.
  
• Drop - Projectiles are affected by gravity.
  
• Close - Projectiles deal more damage for a short time after being fired but have a shorter lifespan.
  
• Homing - Projectiles home in on targets.
  
• Zig - Projectiles follow a zigzag path.
  
• Sniper - Projectiles deal increasing damage with distance.
  
• Multi - Increased projectile count.
  
• Slug - Decreased projectile count. Only found on shotguns.
  
• Burst - Increased burst count.
  
• Accurate - Greatly increased accuracy but decreased damage.
  
• Precise - Increased accuracy.
  
• Wild - Decreased accuracy but increased damage.
  
• Turbo - Increased energy consumption and damage.
  
• Deft - Decreased energy consumption and damage.
  
• Adept - Decreased energy consumption.
  
• Recoil - Attacks knock back the user.
  
• Slide - Makes rockets slide along surfaces.

Melee:

• Hooked - Attacks pull enemies towards you.
  
• Power - Attacks deal more damage but cost energy.
  
• Lunge - First attack in a combo causes the user to leap forward.
  
• Leap - Last attack in a combo causes the user to leap backward.

Shields:

• Tough - Increased health.
  
• Quick - Reduced cooldown.
  
• Robust - Reduced minimum active time.
  
• Flawless - Lengthened perfect block window.
  
• Spiked - Shield deals contact damage.
  
• Potent - Shield knocks back enemies on contact.
  
• Wieldy - Shield can be aimed.
  
• Handy - Raising the shield does not slow the user down.
  
• Powered - User takes less damage while the shield is active but it consumes energy.
  
• Sturdy - User is immune to knockback while the shield is active.
  
• Repairing - Increased shield regeneration rate.

The following mods add actions to shields which trigger when the shield perfect blocks, blocks or breaks.

• Counter - Increases attack damage.
  
• Mending - Generates health..
  
• Innervate - Generates energy.
  
• Aegis - Gives 100 protection.
  
• Mirror - Damages the attacker.
  
• Dread - Reduces the damage of the attacker.
  
• Cripple - Slows the attacker.
  
• Shatter - The attacker takes increased damage.
  
• Confuse - Confuses the attacker.

Armor:

• Glow - Illuminates the area around the wearer.
  
• Featherfall - The wearer falls slower and receives no fall damage.
  
• Grit - Immunity to knockback.
  
• Lavaproof - Immunity to lava.
  
• Swimboost - Improved underwater mobility.
  
• Speedboost - Increased speed.
  
• Jumpboost - Increased jump height.
  
• Light - Reduced gravity.
  
• Bouncy - Become bouncy.
  
• Reflect - Reflect damage back to attackers.
  
• Overload - Create an explosion around the wearer when the wearer runs out of energy.
  
• Tractor - Item magnet.
  
• Capacity - Lowered energy regeneration but increased energy capacity.
  
• Glass - Damage inflicted and taken are both increased.
  
• Turtle - Damage inflicted and taken are both decreased.
  
• Blackout - Energy is permanently 0 but gain attack damage.
  
• Area Heal - Nearby allies are healed.
  
• Area Damage - Nearby allies gain attack damage.
  
• Area Defense - Nearby allies gain damage reduction.
  
• Rally - Every allied entity close to the wearer grants the wearer extra damage and armor.
  
• Repel - Nearby projectiles are repelled.
  
• Sacrifice - When falling below a certain health threshold, nearby allies are damaged to heal the wearer.
  
• Shock - Attacks consume extra energy to shock enemies.
  
• Elixir - Half of damage taken is taken over 5 seconds.
  
• Serum - Take more damage but heal for half of the damage taken over 5 seconds.
  
• Lifesteal - Attacks heal for a percentage of the damage dealt.
  
• Siphon - Energy is consumed to regenerate lost health.
  
• Tap - Health is consumed to regenerate lost energy.
  
• Hawkeyes - Nearby enemies and allies are highlighted in red and green respectively.
  
• Vampire - Attacks heal for a large percentage of the damage dealt but the wearer loses health after not dealing damage for 2 seconds.
  
• Aura - Nearby enemies receive elemental status effects.
  
• Skin - Attackers receive elemental status effects.
  
• Imbue - All attacks inflict elemental status effects.
  
• Thorns - Taking damage inflicts damage to nearby enemies.
  
• Reaper - Periodically zap nearby enemies to heal for damage dealt.
  
• Rod - Periodically zap a nearby enemy.
  
• Immolate - Taking damage equal to 10% or more of your maximum health creates an explosion.
  
• Vengeance - Taking damage while low on health creates an explosion.
  
• Unstable - Final blows create explosions.
  
• Frostbite - Every 5 seconds, the next attack deals additional ice damage.
  
• Ignite - Attacks deal bonus fire damage to nearby enemies.
  
• Plague - Attacks deal bonus poison damage in an area.
  
• Scourge - Every second, 2 enemies close to each other are damaged.
  
• Scorch - Attacks launch a shard of fire towards the target.
  
• Blizzard - Upon landing a final blow, deal damage over 5 seconds to nearby enemies.
  
• Absorb - Gain shield equal to a percentage of damage dealt.
  
• Rupture - Increased damage dealt but dealing damage also damages you.
  
• Cleave - Attacks hit enemies around the target for partial damage.
  
• Fate - Attacks have a chance to deal bonus damage.
  
• Shard - A shard of energy follows you, shooting energy shards at nearby enemies.
  
• Slayer - Getting 10 final blows will cause the next attack to instakill.
  
• Tether - Attacks apply an energy tether to enemies, consuming energy to deal damage. Maximum of 1 tether at a time.
  
• Metal - Gain high protection but lose movement speed.
  
• Smite - Every minute, the next attack causes lightning to strike your target.
  
• Limit - Reduces incoming damage by a flat amount.
  
• Shade - Gain a chain to dodge attacks.
  
• Wraith - Dealing damage makes you invulnerable.
  
• Phaser - Become invulnerable after taking damage.
  
• Nitro - Falling creates an explosion when you land.
  
• Swarm - Final blows spawn friendly gnats.
  
• Splitter - Taking damage flings pellets around.
  
• Avolite - Randomly attack nearby enemies with blasts of energy.
  
• Prism - Every 2 seconds, the next attack fires a beam at the target dealing damage equal to half of the damage dealt.
  
• Horror - Nearby enemies are confused.
  
• Fury - Every 4 seconds, the next attack fires a chain laser.
  
• Devour - Final blows restore health.
  
• Breach - Adds a flat amount of damage to each attack.
  
• Blitz - Dashing deals damage to enemies.
  
• Barbed - Deal contact damage.
  
• Blink - Teleport when hit.
  
• Unit - Every other final blow spawns a friendly drone.
  
• Drain - Attacks apply an energy tether to enemies, consuming energy to deal damage and heal.
  
• Alpha - Increased damage taken from low damage attacks. Decreased damage taken from high damage attacks.
  
• Beta - Increased damage taken from high damage attacks. Decreased damage taken from low damage attacks.
  
• Gamma - Slowly regenerate damage reduction over time. Damage reduction is partially lost when damaged.
  
• Delta - Damage taken provides a fading damage reduction bonus equal to half of the amount of damage taken.
  
• Epsilon - Slowly gain protection over time. Damage taken reduces the bonus by 10%.
  
• Theta - Damage taken provides a 10% protection bonus.
  
• Sapper - Attackers lose damage and movement speed and take more damage for 3 seconds.
  
• Massacre - Kills increase the damage of the next attack.
  
• Obliterate - Attacks hit a nearby target for 1/3 damage.
  
• Annihilate - Every 2 seconds, the next attack fires a laser at each enemy close to the target.
  
• Malice - Deal increased damage to the previous target.
  
• Hatred - Deal increased damage to the previous attacker.
  
• Animosity - Deal increased damage if the target has a weakness or resistance to the attack's element.
  
• Mend - Every 10 seconds, the next attack heals for a percentage of missing health.
  
• Chain - Every 4 seconds, the next attack heals nearby allies.
  
• Delay - 2 seconds dealing damage to a target, the target receives 25% of the total damage dealt.
  
• Breaker - Breakable objects shoot bullets at nearby enemies when destroyed.
  
• Ranger - Deal increased damage to faraway targets.
  
• Skewer - Hitting more than one target at once grants a damage bonus.
  
• Leech - Attacks deal damage equal to a percentage of the target's maximum health and heal you for twice that amount.
  
• Tesla - Every 3 seconds, the next attack stuns nearby enemies.
  
• Panacea - Elemental status effects are positive when inflicted on you.
  
• Relentless - Become immune to slowing effects.
  
• Auto - Attacks summon a drone that shoots at nearby enemies for 10 seconds with a 10 second cooldown.
  
• Roll - Randomize incoming and outgoing damage with a net benefit.
  
• Ancient - Upon receiving fatal damage, instead reduce your health to 1, heal and become invulnerable for 3 seconds. Very long cooldown.
  
• Survivor - Taking fatal damage when above 10% of your health will instead reduce your health to 1.
  
• Blessed - Chance of evading death.
  
• Amplify - Your attacks amplify the effects of elemental status effects.
  
• Frostburn - Apply frozen burning to attackers. Recharged by killing.
  
• Ruin - Upon being healed, deal damage equal to 50% of the health gained to nearby enemies and cause healing to damage them instead.
  
• Powered - Increased defense with the amount of remaining energy.
  
• Brew - Heal 1.5 seconds after taking damage.
  
• Volatile - Successive attacks deal against the same target deal increased damage.
  
• Stim - Gain a huge temporary stat boost when attacking with a moderate cooldown.
  
• Beacon - A mercenary beams down to aid you in combat every once in a while.
  
• Fracture - Teleporting deals damage.
  
• Berserker - Increased attack damage and defense proportional to missing health.
  
• Carnage - Deal increased damage to close targets.
  
• Status - Randomly trigger status pod effects.
  
• Summoner - Spawn friendly monsters when attacking. Killing reduces cooldown.
  
• Shred - Attacks cleave in a line.
  
• Nanobots - Chance to take less damage and heal.
  
• Neo - Spawns an orbiting chakram when using a movement ability.
  
• Synthesis - Reduces energy regen delay when in bright light.
  
• Shackles - Shackle nearby hit targets to you.
  
• Paragon - Spawn a crystal that shields you.
  
• Minefield - Periodically drop floating mines.
  
• Barrage - Getting hit consumes all of your energy to fire seeking missiles at nearby enemies.
  
• Psi - Zap a nearby energy when energy is fully recharged.
  
• Beamer - Teleport to faraway targets.
  
• Orbital - Advanced targeting systems allow you to call down a precision beam on enemies.
  
• Pylon - Spawn a floating entity which is connected to you by a damaging laser.
  
• Torpedo - Delayed strike which deals a lot of damage.
  
• Strafe - Allows you to call in your ship for a strafing run.
  
• Suppress - Stun all enemies onscreen after a delay.
  
• Abduct - Instakill a non-boss target without drops.
  
• Crash - Instakill low health targets.

Outside of stat boosts which aren't named and some special status effects, some armor also gain the ability to generate damage bonuses, movement speed, protection, health, shields or energy for the player. The effects follow the naming of <Resource><Number> and are active under certain circumstances.

• I - Always.
  
• II - Dealing damage.
  
• III - Taking damage.
  
• IV - Not taking damage.
  
• V - Low health.
  
• VI - Critical health.
  
• VII - When healed.
  
• VIII - Standing still.
  
• IX - Movement ability usage.
  
• X - High health.
  
• XI - On kills.
  
• XII - Energy locked.
  
• XIII - Submerged or wet.
  
• XIV - Energy consumed.
  
• XV - Enemy close.
  
• XVI - Not dealing damage.
  
• XVII - Burning, poisoned, frozen or electrified.
  
• XVIII - On ground.
  
• XIX - At night.
  
• XX - At daytime.