The Spectre
The Spectre is built on a Superman base.  I first sliced off the top and sides of his head with an X-acto knife.  I then ground off his boot tops and belt with my Dremel.  I used Sculpey to build his boots and gloves.  The most difficult part of this custom is getting the cowl to look right.  Again, I sculpted it from Sculpey, using trial and error until it looked right from all angles.  Finally, I painted and sealed the figure and added a cape made by my wife.