Shoot down a bullet with a bullet.

Complete all levels of the game.

Kill 100 Red Dudes with a sawed-off shotgun.

Use Mind Wave for the first time.

Kill 3 Red Dudes with a single dual Uzi burst.

Throw 100 objects.

Kill an enemy while not looking at him.

Clear any level on expert difficulty and get at least 500 combo without any modifiers.

Got a hole out

Rescue Jacob from the gulag

Complete any Challenge Tomb

Stealth kill an enemy while they are having a conversation