Counter- Assassin: Kill all assassins.
Blue Shift: Save a scientist from a Barnacle.
Double Tap: kill a marine with a single double barrel blast from a shotgun
bEgon: kill 30 enemies with the Egon
Negative: Say no to Gmans offer
Affirmative: Say yes to Gmans offer
Conversation Stopper: Kill an NPC while he is giving a scripted speech
“Vorts” in session!!: Kill all the voriguants in the game with the shotgun.
You feeling lucky… punk?: Kill a marine with a single shot from a .357, while your health is below 5.
Aperture Science: Use a teleporter to gain access to a secret area.
Get away from there Freeman!: Touch the computer in Anomalous Materials.
Getting outa trouble. Turn off the alarm on Unforeseen Consequences.
Improper Conduct: Steal the ammo from the locker in the Locker Room.
Unwanted Resources: Kill the first guard you meet in Unforeseen Consequences
after he is no more use.
Grabbn’ Pills: pick up 50 medkits in the entire game.
Health Dispenser, Goin’ up!: Drain 10 Health Dispensers.
Master Mind!: Kill a controller with a single crossbow shot.
What did I do to deserve this?: Kill your first Agrunt without taking any damage.
Into the cage: Use the crossbow and cage to kill the first fish.
Maggot!: Kill the squad leader before killing any other soldier.
I spray Osprey: Kill the twin blade helicopter in the chapter Surface Tension.
Tag, your it!: Spraypaint your tag on a wall in every chapter.
I wonder when we will run out of Ideas… 