Coming from Treyarch, Black Ops offers a more realistic, less artificial feel to its sound effects.  Regardless of whether or not this is to your liking, this sound pack is a favorite, because like all Riviera Software productions, it is made of liquid awesome.

FEATURES

Nearly all weapon firing and reloading sounds have changed to those recorded from Call of Duty: Black Ops.  This sound pack is available for both Left 4 Dead 1, Left 4 Dead 2, Counter-Strike Source, and Counter-Strike: Global Offensive.

PREVIEW VIDEO (L4D2)
for LEFT 4 DEAD 2
for the original LEFT 4 DEAD
for COUNTER-STRIKE SOURCE
for COUNTER-STRIKE: GLOBAL OFFENSIVE