I can't really pick just one... for sure I'd toss a +1 vote on Paranoia, Paranoia XP if I had to pick a version of it , but I'd be mainly interested in hearing about what you think about:
1) Deadlands (Savage Worlds version is fine, but I'd prefer Classic)
2) Cyberpunk 2020 (not v3 for the sake of all that's good about RPGs)
3) Slayers D20 (BESM D20 based, I always heard good things about it, but never managed to try it :\ )
Also, but not because I like it, just the opposite, I'd also like to listen to a review about Warhammer Fantasy RPG because I always hear people liking it but I don't see why, from what I've seen and tried it's well... bad. Maybe you can help to shed a bit of light on it. I earnestly want to understand what are its good points as a person really interested in games and game mechanics, but noone of the player I talked with yet has been able to come up with a decent explanaton