Enemy Territory: QUAKE Wars. And if you do get it, please do play it for a couple of hours before judging. When the beta/demo was released, I heard ridiculously many times people say it's just a cheap Battlefield copy; however, most people that said they had played it for a bit longer despite thinking it was a cheap Battlefield did actually seem to change their opinions about the game and they seemed to enjoy the game then.
You might also want to try Quake Live. Don't be scared because it's a browser game; it's basically the old Quake III made work in a browser. Also, you won't lose anything as the game is free.
Speaking of which, Wolfenstein: Enemy Territory, despite being a bit older (2003 to be more precise) could be fun too. And free, if that wasn't clear yet. Yeah, it's also related to ETQW which I mentioned first.
