There are a few items that you can throw around a corner; Grenades, Poisoned Rice, Smoke Bombs, and Caltrops. Put your back to the wall using R1, move to the very end of the wall, and tap Triangle on the item you wish to throw around the corner. Your character will then take out the item and throw it. If it is a Smoke Bomb, the character will cough and you can move in for a stealth kill.