This one's an oldie. I was going to enter it in a 'make your own Marvel/DC character' contest a while back, but I was only half finished by the time the deadline rolled around.

Anyway! Yes. This would be my X-Men fan character. Her codename is Mouse, I think her real name is Abby? I was a huge fan of Christina Weir and Nunzio Defillipis' run on New Mutants / New X-Men / Academy X (the poor comic was renamed about three or four times... I think it's just New X-Men now). It centered on the kids attending Xavier's, with more focus on their personal lives and less emphasis on crazy, world-shattering superheroics. That said, I made Mouse a student, she's supposed to be about 14 or 15, and she's in the Paragons training squad.

Anyway, power-wise, Mouse can hit unnaturally high and low pitches with her voice, and manipulate her vocal cords to imitate certain sounds and voices. Unfortunately for her, she can barely control her powers, and whenever her voice cracks, she hits weird pitches that either make the floor vibrate or shatter windows. Also, she keeps accidentally imitating people. She was pretty shy before her powers hit, and now that she's going through a mutant version of vocal puberty hell, she barely speaks at all.

... Ok, this was a lot longer than I thought it would be. I'm done talking now.