I honestly think Cyberpunk 2020 fits into the Dark Future catergory for it's over-the-topness after a few sourcebooks. It's not the same as SLA (which crosses extensively into Horror territory), but good god, if a game where you can be a chrome-plated cyborg with permanently-implanted mirrorshades hiding independently-tracking eyes (replete with brain-implant to control them) firing two smart plasma-explosion-boosted gold-plated .50AE Desert Eagles modified for fully-automatic fire firing armour-piercing explosive shells and capable of shooting them with accuracy whilst running full-pelt (at 40mph) or jumping from building to building (which your ludicrous cyberlegs make easy), whilst dressed in totally happening Edgerunner clothes, all by buying stuff out of the first few Chromebooks, isn't "pushing the Envelope of Awesome" then I'm not sure what is. And that's only one of dozens of insane plans that work in that game.
Still, in SLA, my character was, by the rules, badly addicted to caffiene and living an armoured personnel carrier full of guns, so I'm not sure if CP2020 ever quite catches up...
I'd second Nightbane/Nightspawn (yes mine says Nightspawn

), for horror, it's absolutely bloody insane. When we played it, one of the characters' Nightspawn forms was a jet-black scorpion covered in steel spikes and transform themselves into electricity practically at will, another was a 9' tall crocodile-man hybrid with cyborg arms and legs, the third a four-winged, multi-eyed aberration, and the last practically a text-book devil, who flew around slinging bolts of darkfire at people. Let's not even get started on how you could have a motorcycle for a lower body if you rolled right (or wrong, depending on perspective!).
The thing about horror, is though, that the mood is ruined by things being over-the-top and insane.
However, that didn't mean some games didn't "go there".
Werewolf: The Apocalypse (not the Forsaken), 2nd Edition, was complete and utterly off-the-rails, giant werewolves running screaming at each other with silver "klaives" and grand klaives (think very big knives), mutated monstrosities all over the place (Fomori), a fundamentally ludicrous corporation whose only purpose is to corrupt the earth, and let us not forget "Hoka hey!". I'm not sure W:tA 2E *meant* to "push the envelope of awesome", but it ended up this way.
Also, am I high, or did you not list RIFTS? No "pushing the envelope of awesome" can POSSIBLY not have RIFTS on it. I mean come on! Glitterboys, Dragons, Futuristic Nazis, Cyborg Jedi and men who can set fire to you with their minds, and that's just the first book! Later on we get every kind of possible vehicle, no matter how insane, the chance to play gods, demi-gods, psychic worms, druids, vampires, giant indestructible tigermen with insane powers, Atlanteans covered in magic tattooes that make them so tough they can take a tank shell in the face, and oh god I could go on ALL DAY.
It could fit in Dark Future or Fantasy, or both.