I want a game that i can knife people in or stealthily kill them

[Dioxinis]

So i want a game that i can sneak up behind someone and stab them in the back or some other such stealth assassination. it has to be for a purpose though.

its no fun sneaking up on people in assassins creed and assassinating them just cause you can. i want it to help me progress through the game.

please no splinter cell as i didnt care for the games.

 

if metal gear solid has this let me know cause i've never played them but i KNOW i need to but if it has this i may bump it up on my list of games i need to play.

 

thanks in advance :D