This is definitely Left 4 Dead. The first thing that hit you'll notice is the gore, the zombies in the first game were bloodied up but not to this extent. Missing arms, glistening gore covered chests and this is before you shoot at them.
(Left 4 Dead 2, PC, Xbox 360)
80°
70°
180°
120°
Ad 
170°
10°
40°
20°
10°
20°
