Kuma has already brought up Alternity.
d20 plus or minus a step die, to roll under an attribute (iirc).
I would also like to bring up d10x, the method of rolling dice from Cyborg Commando.
Roll two ten sided dice, and multiply them, to get a number under a skill rating.
I tried playing Cyborg Commando once and couldn't figure out what the PCs should be doing so then I tried repackaging an adventure that seemed to work when we were playing Living Steel, but then we got confused and stopped playing.
None of that was the fault of that game's method of die rolling.
I'm not saying that I would like to see retro-clones. Retro-clones might be cool, but so would new games that just use these odd methods of producing random numbers.
Would anyone volunteer to use one of these systems? Would anyone like to nominate another weird system for resurrection?