Some fun blue multiplayer stuff off the top of my head... One guy I know built a deck that used Rhystic Deluge and Cowardice for fun creature bouncing. He also built a deck based around Sunder and Blood Oath... I've seen decks that used the Thalakos creatures (along with the Dauthis) and some blue support. Phasing can be awesome. Stasis. Well, that's only fun if you're particularly deranged. I built a High Tide deck that was pretty annoying in multiplayer. The most awesome multiplayer deck ever, Relentless Pony, uses no color other than blue (in the maindeck). Zur's Weirding. I've seen some oddball Wizard-based decks that worked decently in multiplayer.