I almost forgot, there are some unique stealth kills that are unknown to some players. Here is a list of all the stealth kills:
~ Behind the enemy.
~ In front of the enemy.
~ Above the enemy (air stealth kill).
~ Below the enemy

(you must be hanging from a ledge).
~ Downed enemy (enemy must be lying on the ground).
~ Large enemy stealth kill (just get behind any big enemy; bears, barbarian chief)
~ Water stealth kill (sneak up on an enemy in the water).
~ Enemy picks up an item (get the enemy to pick something up at the same time you press triangle for the stealth kill, timing doesn’t have to be perfect)
~ The wall stealth kills (back up against a wall, move along to the end of the wall and if there is an enemy around the corner [he/she has to be close] you can do one of the two wall stealth kills, one from the left and one from the right)
~ The door stealth kill

(enemy must be on the other side of a closed sliding door, you won’t be able to see him/her until you stealth kill them).