I kind of like more of the underdog story, although I think everyone likes that. But it highly depends on the roleplay. If its a roleplay supposed to be with normal people, I usually make just a normal person. They might be really good at one or two things, but nothing really important that would help them a whole lot in the game. More just quirky talents to brag about but don't actually do anything.
However, in RPs where powers actually are a factor, I try to create characters with what I think are cool powers or abilities, but at the same time have some fundamental drawback. It's no fun if you can just play god with superpowers, there should be some weakness. And the more the weakness affects your character, the more inventive and creative you have to be when it comes to your posts.