There's always The Hidden: Source, which is basically Predator in game form. There's one team of IRIS operatives versus the eponymous Hidden. IRIS has numbers and equipment, whereas the Hidden's very mobile, strong enough to one-shot with his knife's alt-fire (only a limited number of times per round based on player numbers, for balance) and almost completely invisible. As he's only armed with a knife and up to three pipe-bombs (again, depending on IRIS' team number), he's got to be tricky in order to pull out a win.
Fun things to do include feeding on dead IRIS soldiers to regain health, grabbing their corpses and pinning them to walls, or just jumping around with the body and then dropping it in front of a guy who's all alone and watching him freak the hell out. On the other hand, playing against a good Hidden is an exercise in tension and paranoia, because LOOK OUT ABOVE YOU, oh no, it's too late, he hit you with a pigsticker stab and is now using your giblets as a macabre art-display.
Also, IRIS doesn't get notified when their teammates die, so if you get stuck all alone for a while there's a good chance everyone else will be too dead to answer your radio request for them to report in. Enjoy the pants-wetting terror of rounding a corner and seeing everyone hanging down from the ceiling!*
Sadly, only a few people play it anymore, and the mod hasn't updated properly in about five years or so. Valve's updates to Steam have broken the in-game server browser, too, so you'd have to use
Game Monitor's server listing to get into games. Then, seeing as people are mostly using custom maps now and the game doesn't let you download them by default, you'd have to finagle around with the ingame dev console. Also, it requires any Source engine game, but that part's pretty easy to handle.
In game, go to Options -> Keyboard tab -> Advanced then check Enable Developer Console. Hit ok then hit your ~ key which will pull up the console. Type cl_allowdownload 1 and cl_downloadfilter all in the console.
*
Not actually sure it's possible to pin people to the ceiling.