Darth vader, Gollum, Sauron (and pretty much all the bad guys in LOTR), The Covenants in Halo, Rat creatures (in the Bone series), that's all I can think of for now. Their are many more villains that I like but I didn't know of them until I became much older.
I used to have that movie, and I used to have the game, it might be in storage even... The book as well. I was a huge nerd for these guys... Air rules all!
1: The Joker 2: Kain, from the Legacy of Kain series. Number one doesn't need any explanation, but number two has always been interesting for me. Since -- Spoiler! -- The guy you played a couple games as, and then a couple games hunting down as his seemingly wrongly-executed-and-reborn former vampire son, was a good guy all along. A proper bastard, but a hero.
too many comic book villains to list. some that haven't been mentioned yet: kingpin, green goblin, magneto, venom, thanos, basically every batman villain, doctor octopus...the list goes on. honestly, one of the greatest villains of all in my book... is Arthas Menethil. The Lich King of The Scourge. forget WoW. Warcraft 3 was incredible and awesome. and dat story. also darth vader is a legend, along with lord sidious, darth bane, sauron, saruman, every ring wraith, hal 9000...i could go on... abbadon, horus, the emperor, eldrad ulthran, the chaos gods, the nec--well, every single race in 40k and all the major players in them... yeah..
Childhood villain? Hrm... Probably Darth Nihlus, from Star Wars: Knights of the Old Republic II: The Sith Lords. I was obsessed with that game (still am, honestly). It drove me crazy I couldn't see what was beyond that mask, even after I took the mask from him!
I'm not too sure, to be honest, but I guess my favourite has always been Curt Connors (a.k.a. the Lizard) from the 1994 Spider Man TV series. I also liked Venom from the same series; I think he was a rather interesting character.