That's a Knife

That's A Knife is an achievement in Halo: Reach. To unlock this achievement, a player must perform an assassination on an enemy.

Tactics

 * The easiest way to get this achievement is to play a Forge game with another person, have him stand still, and perform the assassination.
 * You can also play Nightfall, as the first few enemies you encounter are an Elite and two sleeping Grunts. Any of the Covenant idling there may be eliminated with ease.
 * You could also do this in conjunction with the If They Came to Hear Me Beg achievement.
 * Another easy way to get this achievement is to assassinate one of the sleeping Grunts on Corvette.

Trivia

 * The name of this achievement references dialogue from the film Crocodile Dundee.