Left 4 Dead 2.
etc
does aim even really matter in L4D? like, I'm sure there's a difference between head and body shots. but does it differentiate between torso/waist/leg/etc.? in bf3, for example. I know it does. like with a crossbow, if you hit them in the head or chest with a regular bolt, it's a one-hit kill. but anywhere else, it takes two (which is a REALLY bad idea bc of the super-long reload). so you really have to focus on getting chest, because trying to hit the head is unreliable unless they're standing still. and I think that's really interesting, the whole re-learning thing. but otherwise, using firearms, my aim usually starts at the chest, and naturally drifts up to the head from recoil, but also on purpose, bc it'd be easy to keep it on the chest if I wanted to :P