I think the ultimate"glitch" would be Raider's of Lost Ark on Atari 2600. In order to get out of the title screen you had to have the switches on 2600 in certain positions. You can only imagine how many minutes/hours I spent staring at the balloon flying title screen. I actually was able to start the game a few times but we only had cartridge and no instruction manual so I was never aware of how I actually got it started. Oh and when I finally did get to play the game a fucking crocodile or snake would insta kill me.
Kids these days.... Have it too fucking easy.
I never did figure out how to beat Raider's of the Lost Ark, and it wasn't from lack of trying. People complain about E.T., but E.T. was awesome compared to Raiders of the Lost Ark. At least the gameplay of E.T. made sense to my 7-year-old self.