I don't know about anyone else, but I really enjoy glitching some games out, so I've decided to start a topic here where everyone can share some of there favorite glitches.
I'll start with a well known one.
Pokemon Red/Blue: Missingno.
If you talk to the old man in Veridian City who shows you how to catch a Pokemon, watch him catch it, then fly to Fuchsia City and surf down to the Seafoam Islands and surf along the side of the first island you will encounter Missingno. or one of its many forms. Encountering Missingno. will cause the item in the 6th slot of your bag to be multiplied by a large number (I think its something like 126)