Well, as someone mentioned, Mystique would be perfect for any trans or gender-non-conforming person.
But I still have a lot of residual anger:
I have always related to Magneto, even before I came out. Here's someone who has had the world try to exterminate him and his people TWICE. With the conservatives trying like hell to remove people like me from public spaces, deny healthcare, etc, I can relate a bit, although obviously not on as grand and terrible a scale.
After X-Men apocalypse, every time I heard of yet another legal/social blow, I kept hearing the line running through my head, "Everything they've built will fall..." And I can only hope that becomes true.
But on a less serious note, I notice people have diverged a bit from x-men here. If I could pick any power, and lived in a universe with other powered people, I'd choose Sylar from Heroes. Stealing the power of others to make myself stronger!