Sean Cassidy

Banshee is a mutant.

X-Men Origins: Wolverine
He makes a brief cameo as a prisoner of William Stryker in his mutant testing facility on Three-Mile Island. He, along with the rest of the incarcerated mutants (Quicksilver, Emma Frost and Cyclops), escape with the help of Professor X.

Trivia

 * In the film X2, his name along with his daughter's appears on a list of names Mystique scrolls through on Stryker's computer while looking for Magneto's file.