Have you heard about this new game called LoadOut?
It is a new F2P - FPS with a cartoon flair. You can find it at Loadout.net and there are keys all over the place to join. Only available on Steam. It is also over the top graphic cartoon violence.
So everything is customizable... no one gun here and there, you build your gun however you want... guns, launchers, sticky mines, fire bombs...
It has a very fun feel to it similar to Team Fortress. The game is seriously fun.