3 Pokemon Glitches:
Missing No., Glitch City, and the Mew Glitch.

Also, there was some way to use Aeris on Discs 2 and 3 on Final Fantasy VII, but I don't remember how to do that one.

Didn't we have a thread just like this like 2 weeks ago?

I liked the secret weapons in POP : warrior within , where you could use a Mickey glove as a weapon :P

 Maybe, maybe not.

In The Temple of Elemental Evil it seems that troika knew some munchkins would get a lil click-happy with the roll feature... so when you hit 99999 clicks... it says instead of roll count ''Enough clicking already ALL 18's!''



....
here's the fun part
....

click again...

''Not good enough, fine... ALL 3's ''

 Yeah, I remember those =P they screwed up my blue version because I used them so much lol.

I also remember a glitch in Advance Wars where you would be able to delete enemy units in campaign mode, allowing you to win in one turn.

The JP glitch in final fantasy tactics. You can get all the abilities of certain classes at level one without gaining like any EXP.

The class had to have more then like 10 abilities or something though...Also when you did it for the summon class and got all the abilities it doesn't show that you mastered it even though you got all the abilities.

In La Pucelle tactics there were a few movement related glitches that were beneficial

http://www.gamespot.com/ps2/rpg/lapucelle/hints.html?mode=glitches