Zombie Edition is a Half Life modification, first person shooter game where you play as a headcrab or zombie. Some will find it interesting, others will get bored but this title will at least make the fans curious to see what it's like to be "on the other side" of the barricade.
Life as a zombie is tough. You often have to eat human flesh just to live otherwise your body rots away and you become a headcrab again. That makes you very vulnerable so you need to find a host. You need to sneak on to somebody, jump and attach to his head. This will result in mutating and getting control of that person.
The idea is simple enough for those familiarized with the Half Life world. The game is free so if you're interested, you can give it a try.