I don't see why "invulnerability" needs to be #1. Can't believe only one person before me said it..."supernatural luck" is a solid #1 pick. Strong enough, and it's all plot power you need.
Oh god a bullet is coming my way and I'm stuck in quicksand with no place to go and no way to stop it! *crash* phew, lucky that elephant just fell through the roof and took that bullet for me. Etc.
#1 Supernatural luck (I might actually get lucky)
#2 Ability to change someone's feelings (make someone instantly happy, instantly sad, depressed, angry, quiet,....) (basically a stronger but lessp recise form of mind control I guess) -> both a strong offensive power (all enemies are suddenly overcome with crippling anxiety/depression/suicidal tendencies/a moral imperative to become a Zen monk/terror/....) and a great team power (what do you mean you feel "down" or "not very creative" today?), plus, making all the ladies hot for you must have some sort of advantage.
#3 Timelessness (time stopping, no aging, fast forward, super slow motion etc) (and the ladies will think I lasted more than 2 minutes)
#4 Complete shape shifting (including changing mass, tensile strength, etc) (plus I'm insecure and want to increase my endowment)
#5 Some form of pain/damage/health issue/etc prevention (because STDs suck)
...what?