7 Eldrazi Conscription Akin to creatures out of Lovecraftian horror, The Eldrazi are cosmic horror creatures from the Blind Eternities, first appearing in the Rise of the Eldrazi set in 2010
You can also probably get away with just running one copy in the deck if you have a card you use to add a little utility or support to your strategy, or one that you use as your silver bullet against certain strategies that are more common in the metagame
Were already seeing Zendikar Rising experiment with using different card types as the front side of these, which will affect deck-building and combo options across various formats (the front side determines how you can search for or target these cards when they arent in play)
Gengar H9 has a powerful attack that either burns or confuses the enemy Pokmon depending on the coin toss, but more importantly, it has the Pok-Power: Manipulate, which allows the player to place a basic Pokmon from the discard pile onto their bench and flip three coins to determine the amount of energy cards the player can attach to said Pokmon from the discard pile
Ulalek also has a ridiculous ability in terms of complexity and power level
Hedron Fields of Agadeem I like the tension that Hedron Fields of Agadeem provides since the big creatures cant enter combat, but hey, if chaos ensues you get a free 7/7 with annihilator 1