Kuriboh can be a lifesaver sometimes.
I haven't played in a long while either, but that Earthbound guy sounds like the Chuck Norris Card to me. Hmm... when I used to play, there was one card. Can't remember it's name, but it got 300+ attack for each monster in the graveyard, so I'd just purposely sacrifice my monsters for high defense monsters, then I'd summon that thing with 4200 (14 monsters in graveyard) attack or something, and my sister surrendered =D
The other one was Maha Valio (probably spelt it wrong; the monster with 1550 attack that gained 500 attack for each equip card you put on it). That thing was insane, especially with a ton of attack raising equip cards.
Dunno if either of these are forbidden/limited...