iGun - MW3 Edition is an app that has a majority of the guns in MW3, that make sounds when you tap the gun. It includes some of the noises in MW3 and some made in real life.

GUNS INCLUDED:
44 Magnum
Barrett 50 Cal
M16
Skorpion
Water Gun
M1 Garand
Ray Gun
RPG
AK-47
Desert Eagle
ACR
M4A1
PP90M1
Scar
Knife
NUKE

Explosives:
Flash Bang
Frag Grenade
Dynamite
Smoke Grenade