Excellent idea man! Here are the first ten games that have come on my mind.
•
Ancient Domains of Mystery/ADoM (or its fellow
NetHack; both are PC/freeware) — not sure if they generally are weird, but both of them have tons of, well, really strange things (imagine a level full of the killer bunnies for example);
• Carmageddon (PC/commercial) — well, it made a revolution successfully turning a racing game into something that doesn't actually resemble racing at all, not even a little bit.
•
Darwinia (PC/commercial?) — weird storyline and graphics.
•
Destruction Carnival (PC/freeware) — very funny Smash TV clone with ridiculous graphics and MIDI music ripped off some games like Mega Man, Super Metroid, Axelay and others. Probably win9x only.
•
Dungeons of the Unforgiven (PC/shareware? more like freeware, actually) — just look at the
screenshots, and add this to the Honourable Mentions section ASAP!
• Exile
1/
2/
3 (PC/shareware) — the series don't really look weird until you actually start reading some text messages and listening to the game sounds (Exile 1 splashscreen sound is just priceless), not to mention some monster sprites. All three games, however, are VERY cool, thoroughly made and really interesting to play.
•
Jumper! (PC/freeware) — a game with ridiculous story and, as a result, even more ridiculous main character.
•
RAM: Rural Anti-alien Militia (PC/freeware) — quite a moronic game with nice sound effects. Probably win9x only.
• Sensible Massacre (Amiga/commercial) — more info
here.
•
Triptych (PC/shareware) — a hybrid of Tetris and Bejeweled, based on a physics engine (that is, with gravity and control over the figures' movements).