I have two favorites, with the former edging out on the latter by a bit, but I still want to mention both. Incidentally, while both are from completely different developers and publishers, they both made their first appearance in a Smash game together with Brawl.
Wario
Don't let his usual butt-scratching attitude in Mario games fool you, Wario is much more than that and it's VERY evident in both his gaming series, Wario Land and Warioware. Although in typical Mario games, he's just a guy with gas coming out of his back, he's a completely charming, hilarious and lovable character in his own franchises. Most iconic heroes are bland compared to this greedy, irresponsible man, who does things his way and only for one thing - money. In the Wario land series, he only saves the day by
total accident.
He's a completely fresh breath of air from your typical hero. Mario, Link, Kirby, Sonic? Boring. Wario is the real deal. I've yet to see a character so greedy and selfish with pride and ego to boot, yet so charming, clumsy, hilarious and in a sense, relateable. He just wants things for himself, who can blame him? He's not harming anybody!
Solid Snake
The epitome of
BADASS. This dude is the personification of a high IQ killing machine. He's calculative, careful, intelligent with a strongly developed sense of justice to do what is right even if it means sacrifices, and he still thinks murdering is wrong regardless. Honestly it's all pretty self-explanatory.