The glitchiest non-mario game has to be Pokemon Red & Blue. Missingno, which gives you more than 100 of one item, the Safari Zone Warp glitch, where you get out with the time still going, walk around, get sent back, and get stuck in a warped world where you can stand on water by pressing start. You can even get a level seven Mew! (Got to the underground path, Lavender side. Exit and step one south. Pause before entering battle with the gambler, fly to Cerulean, fight the kid with the slowpoke to the north. Fly to Lavender, walk onto the route where the gambler is, and your start menu will open. Press B to see a wild Mew at level seven.
You can put a spoon between two slices of bread and it only sticks out a little bit! –Andy Milonakis