The original developer blog talks in depth about trying to balance a realistic feeling with what players will expect from guns, but the follow-up goes into more detail. Gunfire and sounds will indeed attract zombies to players, but the team doesn't seem interested in burying players under mountains of different ammunition types. The guns in question will most likely not be licensed brands, although some licenses are being sought for some more iconic weapons. There also won't be a full spread of exotic firearms in the console game, Class 3, although the MMO version will likely have a wider variety. Take a look at the full set of answers for more details on the best part of zombie invasions -- sweet, sweet hails of bullets.