These freesound.org users are credited in the game's credits as contributors to a portion of these sounds:

anamorphosis
chipfor
jascha
Leady
m_O_m
PhreaKsAccount
sandyrb
stickman
zimbot
benboncan
guitarguy1985
joedeshon
LG
mich3d
Pogotron
shakaharu
thanvannispen
cdrk
HubOfTheUniverseProd
Jovica
loofa
Percy Duke
Rock Savage
sirplus
virotic