Hitman: Absolution - It's All In the Wrist

This achievement is exactly what it sounds like - you need to get a kill using a thrown weapon. The only other condition is that it must not be on the first level or it won't count. This is likely so that you don't rack up half of the achievements in the game while you learn how to play.

So just start on King of Chinatown and take a knife from any of the cooking vendors. Use the LT/L2 to aim and when the arc locks on to the target's head with a red circle, pull the RT/R2 button.