Let me think about this... Well, shape-shifting would
be fun, but I can see it getting kind of boring after a while. And Pride's controlling of shadows is really badass, but I honestly can't think of many good uses for it in the long run. I find the other ones kind of stupid, so I guess it's down to Wrath and Greed.
Wrath's ultimate eye would be SO useful. And Greed's ultimate shield would be awesome too, 'cause I could just jump off of buildings all the time and not worry about breaking my legs. That'd be pretty sweet xD
Although now that I think about it, Greed's shield isn't just for defense. He also uses it for unarmed attacks. I guess you can't beat that... I suppose I'd go with Greed then!