Wraith
Hector Rendoza, better known as Wraith, made his debut in The Uncanny X-Men #392 and left quite an impression on readers. His mutant ability to turn his skin transparent and also temporarily make others transparent too.

The only time Wraith proved his worth was when he extended his invisibility field to confuse Magneto in a fight, but for the most part, all he did was scare people out by being a walking, talking, muscle-covered skeleton.