Molez

Molez is a single screen, 2-4 player, real time gun fest. There are quite a lot of weapons to chose from, and they are balanced out quite well. As well as weapons there are 3 different landscapes to chose from, although the only difference they make is to the appearance of the level. This latest version of the game offers a few new weapons, and gets rid of some of the old (crap) ones, the biggest difference the new version makes is the option to have a 4th player.
http://www.free-games-net.com/games/molez.shtml