Dark Henchmen ftw.
I've only played Timesplitters 2, but it's an incredibly fun game. The arcade challenges are usually good fun (and almost certainly a challenge in 'Elite League'). I had two parties a couple of weeks ago and Timesplitters 2 pretty much dominated both of them (though SSB:M was also a favourite). Such great fun in multiplayer. Though when a friend of mine made a MapMaker level based on a rave, there were many headaches when played with the lights off!