Usefulness:
Boredom -| - - - - Pwnage

This takes some practice and is best done in the homeworlds. The trick is to get to one of the top corners of the screen on a really high platform, and try to glide into the corner or side edge. The homeworlds are the best to try this in, as it can take several tries and would usually drop you into the water that surrounds most of the levels if you fail. Try approaching the edges and corners at various angles, making sure you keep the buttons held down like you're pushing your way in. Eventually Spyro will find the dead-spot and slip into an invisible glitch area that lies "high" above the level; you can walk around above everything! It's not very useful for navigating a level; the walkable areas tend to be above water and some low-lying areas, and trying to walk forward when Spyro meets an "edge" will often result in him falling. And I do mean falling; in some areas you can be halfway up the map, but if you fall off you'll find that he was actually above a spot 1/4 above the bottom of the map. However, up there you're obviously immune to enemy attacks, and I've been able to breath fire at them in safety by walking "next" to them and blasting them.

This glitch is more for boredom's sake than anything else, so don't waste your 99 lives trying to use it to navigate a level :P