My Game Idea:

A zombie hoard game! Now I know you're thinking "there's tons of zombie games out right now". I'm not proposing a survival horror game. I'm proposing a game where you ARE the zombie!

Here's how I would envision it:

Scene: The start of a reanimation virus outbreak (and being as the outbreak just started, widespread news of it is minimal). You are one of the first few to be turned. You start out as the "slow walking" zombie type, with limited actions at your disposal (mainly just drag your leg and bite). 

As you start feeding and infecting citizens, the news spreads and panic arises. The more you feed, the stronger you get (gaining speed, some cognitive knowledge, etc..). Also, the more you feed/infect, the more chaotic the citizens get. Every time you feed, shortly thereafter your dinner becomes one of your infected hoard. More infected means less to feed on. If you're killed (by citizens, police/military, or other zombies), after a re-spawn timer you would take over one of the infected from your hoard. If your hoard is eradicated, it's game over for you.

Now on a competition standpoint, the winner would be the hoard that is either biggest by the end of the match or the hoard that ends up killing/eradicating all other hoards. There could also be "capture the flag" type of game, where the goal is to capture citizen strongholds. You could also have one team be the zombies and the other be citizens. A beast vs. Man scenario.

As far as weapons/abilities, once you have infected enough citizens, you as the Alpha start mutating, and gaining new abilities (like spitting infected blood, zombie dogs, etc..). On the citizen side, as more are infected, widespread chaos ensues, which increases the threat factor. With a higher threat factor the citizens gain increased ways to fight off the hoard and defend themselves (i.e. starting off just screaming and running, then police, then local militia, then military. at the 5 minute left mark a nuke is called in).Each starting zombie player is a different strain of the virus (signified by a different color, symbol, etc..). If you kill an infected zombie of a different hoard, that zombie converts over to your hoard.

There could be temporary power-ups that not only affect you, but also your hoard, like give them increased speed for 30 seconds, or give them "terror" which makes other hoards run away in fear for 30 seconds.

The name of the game would be Feed>Infect.