Serious Sam is a very strange game. A crazy, funny, and absolutely crazy game. You basically have to obtain weapons, armor, health, and ultimately extra lives by beating enemy waves. It's a little old-fashioned, but it still pulls it off with flying colors. If you love shooting games with a ridiculous premise, than Serious Sam is for you.
The game starts out with Serious Sam (as he was known in the first game), who has somehow landed in the underground facility. There are two things that happen in this levels - you have to fight your way through and protect yourself from the infected enemies and the endless waves of the zombies. The goal is to stay alive as long as possible, while doing so you must collect as much ammo, health, or money as possible. It's a perfect mix of puzzle and shooting. Although the puzzles can get very easy at times, they are still very challenging and often require lots of thought.
The story line is very interesting and gives you the full zombie experience. The overall graphics and game play are just above average. This game is available for both PC and the Xbox, which are pretty good. Although it seems like it would be better on a console, I feel that the PC version is the best. Either way, you should look into this game if you haven't played it before because it's a great game that you won't soon forget.