Loadout:
Shotgun / Bullpup Rifle
Grenade Launcher

Squaddie:
Blast Padding
Launch Grenade

Corporal:
Flash Round (Take a shot with +15 aim, does no dmg but can disorient a target)
Sapper (+1 dmg with grenades)

Sergeant:
Breaching Round (destroys cover)
Remote Start (blow up environmental objects and make them do more damage)

Lieutenant:
Flechette Shot (deals -3 damage but is a wide accurate shot over a wide area)
Heavy Ordnance

Captain:
Ever Vigilant
Volatile Mix

Major:
Storm Position (dash up to an enemy and attack them with your primary weapon)
Salvo

Colonel:
Explosive Shot (Deals double damage & ruptures a target)
Shredder Blast (Destroys cover and damages enemies in a wide cone)

GTS:
Biggest Booms (gives grenades a 20% crit chance)