I kinda think Lara Croft is quite sexy, even though she's not strictly a "superhero." Not in a perverse way, I'm more attracted to her strength of character than anything...
Other than that I like Wonder Woman and Witchblade.
I second Madman's point - is this just to talk about how "hot" a given superhero is? Because that's not a good axis of discussion for this family-friendly forum. You can discuss who you like and why, but let's keep the discussion away from bulging muscles and - other body parts.
It's also in the wrong forum, so I think I'll move it.