ZENO CLASH / Ace Team / PC
Somebody managed to make a beat-em-up with the Source engine? Yep ... but they didn't stop there! They set it in some post-apocalyptic, Mad Max wasteland full of delightfully insane mutants. They made it look really, really nice (in a mid-2000s sort of way at least) and gave it quite a decent soundtrack. And then they wrote some insane, drugged-out, nearly incomprehensible story for it, made all the more hilarious by weird dialogue delivered in mumbly tones that you can barely understand.
Basically it's Turok: Mutant Puncher. You play as some guy named Gak, and apparently he and his girlfriend are the last two sane people left on Earth. Though Gak killed his tribal leader, a character called Father-Mother, for some reason (that isn't explained until well into the story), and is now on the run from the surviving members of his tribe. And apparently Father-Mother was literally the father and/or mother of everyone, because they're almost all really freaky inbred-looking mutants.
This plays out basically in a series of self-contained little action levels; you usually don't carry anything between them, nor is there any kind of level-building or anything. Gak primarily brawls with the foes in WASD first-person style - left button for a weak punch, right button to wind up with a strong punch, and the space bar to block and dodge incoming blows. There's a bit of a Punch-Out quality to the brawls, but weapons also come into play sometimes too. There's various guns to pick up, but they're as unconventional as the game's setting ... often they're actually not very effective, and enemies can still rush you while taking multiple shots from them. If an enemy melee hits you while you have a gun equipped, it automatically goes flying. The guns also have very limited clips and a lengthy reload time.
Unfortunately, most of the difficulty comes simply from enemies constantly spawning in behind you and taking cheap shots at your back while you're engaged in a Punch-Out dukefest with some other guy. I got fed up with the only challenge coming from ridiculous backshooting about halfway through and never bothered to finish it, but I still think the game was worth the $1 I paid for it (on a Steam holiday sale) just for its various unique qualities and unintentional hilarity. I've been gaming for about 25 years now and I'd estimate played a good 2000 of them during this time; I'm rarely surprised by the medium any more. But this one managed to do it. Interesting work Ace Team. Needs some serious gameplay polish in some areas, but very interesting work all the same.