Halo 3 Spartan Jumpsuit

"Sometimes the UNSC deploys to planets with a greater gravity level that regular. To combat those weighty effects the ‘Jumpsuit’ was created for Spartan troops. This armor-integrated acceleration system raises the Spartan’s mobility in heavy gravity conditions and allows him to leap greater distances in normal gravity, bordering on near-flight. This particular system was soon integrated into the popular sport Grifball, allowing expansion of playing fields and bomb-dunking techniques"

Not in any Halo 3 game or novel, the Jumpsuit Spartan was created using a McFarlane Master Chief, back fins made from the legs of a TF Beast Wars Megabolt, and arm lasers from a Microman bug-vehicle kit.