Loadout:
Sniper Rifle
Pistol

Squaddie Perks:
Squadsight - Can take shots at enemies allies can see as long as you have line of sight.
Stillness - Will remain concealed on squad reveal and is harder to be detected by enemies. Can also re-enter concealment 2 times per mission.
Gunslinger - +1 Pistol Damage (and also confers the Fire Pistol Perk)

Sharpshooter Tree:
Snapshot - Take a sniper shot after moving but at a -15 aim and crit penalty.
Bloodtrail - Shots against enemies wounded this turn deal +1 damage.
Deadeye - Attempt a low accuracy shot to deal double damage.
Death From Above - Kills from high elevation cost 1 action and do not end your turn.
Clutch Shot - A pistol shot (can use squadsight) that has 100% chance to hit
Serial - Activate to have sniper kill shots refund action points.

Spectre Tree:
Vanish - Can move to any location within allied line of sight. Uses 1 charge of stillness.
Shadowstep - This unit no longer triggers overwatch.
Silence - Take a shot that doesnt break concealment, requires both actions, has cooldown.
Shadowstrike - Shots form concealment get +25 aim and crit chance.
Mute - Provides 2 extra charges of stillness.
Shadowfire - Sniper shots that kill enemies no longer break concealment (but not snapshots)

Gunslinger Tree:
Shadowshot - A pistol kill with this shot will not break concealment.
Fast Hands - Grants Quickdraw and Return Fire
Pot Shot - Take a free pistol shot with low accuracy but it deals double damage.
Faceoff - Fire your pistol at every visible enemy.
Wounding Shot - A pistol shot that ruptures a target, making it take +2 damage from other attacks.
Fan Fire - Fire 3 pistol shots at a target enemy.

GTS:
Focus Fire - +10 aim and crit bonus.