Giant Spider / Sea Monk / Ghoul + any Attacks First item
The mirror-image of Attacks First creature + Ghoul's Claw... now you have pseudo-Nikes all over the place!
Thunder Beak + Gem of Life
Your victim pretty much has to neutralize you and kill you (or smash the Gem) to stop mutual destruction from happening. Yeah... good luck with that!
Bistair / Selenear + Arcanum
Yeah, you can only do this once (all 3 are E cards), but... 80ST scroll attack and Mudman's in-battle ability. As if 80MHP isn't enough already!
Ormec Head + Pot of Souls
MHP -10 at Battle End? How about MHP +10 instead? Thank you, come again!
Deep Spawn + Pot of Souls
Stay awhile, won't you?