Delirium - If there are four or more card types among cards in your graveyard, instead that player sacrifices a creature and a planeswalker of their choice
I could devote an entire post just to this addition, and how Esper (White/Blue/Black) Zombies can now be explored as, at least, a fun casual deck
I actually emailed Wizards of the Coast and got their permission to share a free printable
While incredibly situational and requiring a lot of mana to be left on the board when you pass the turn, which is sure to raise suspicions with your opponent, if you can pull off this spell at an opportune time when your opponent has used up all their mana, it can be completely demoralizing, effectively making it so they may as well have skipped a turn
This friendly bunny buffs your board while giving your opponents cards, which admittedly sounds like a bad deal, but you get so much more value
When I first turned in my design for Mirrodin , Bill Rose, the head designer, felt I had too many mechanics