http://www.moddb.com/mods/the-haunted

It's basically a non-linear L4D-like UT3 mod. It's actually pretty well done for a mod. The gameplay seemed somewhat vague, albeit I just jumped in without reading the instructions (pfft. who needs instructions anyways). But seems to be on the same basis with the invasion gametype for those who remember it in UT2K4, just with demons instead of monsters (same thing really, though demons are monsters with a purpose. Usually the purpose means tearing out your innards and wearing it around their necks in a way that an undead Mr. T would approve of, but hey.. I'm not one to judge).

Survive the waves of increasingly tougher demons(read: zombies) until you die. There might be a timer.. I didn't live that long to find out. And there is also a versus mode. *shrug* Seemed pretty fun from what little I played. Just something new to try I guess.

Trailer