Wolverine’s fast healing ability. I remember this episode of X-Men TAS (season 2, Time Fugitives) where Cable let Wolverine be infected with Apocalypse’s virus. When healed, Wolverine’s antibodies was studied to cure the plague affecting Bishop’s time.
As a kid (pre-grade school), I was fascinated with me being doctor. Later I found out that I don’t like the sight of blood and I am not a people person. I also fantasized being an astronaut but, come on, I was born on the wrong country.