Mox Jasper There couldn't be anything else at the top of my list besides this 0-drop artifact that taps for any color of mana if you control a Dragon
If your life total would be reduced to 0 or less, instead transform this creature and your life total becomes 3
"You flip a coin target opponent calls Heads or Tails", that's fairly straightforward
Provided you have a way to discard cards, this lets you cheat massive creatures with powerful abilities into play, even cards with clauses that cause them to be shuffled back into your deck when they hit the graveyard (like the MTG Eldrazi titans)
While this Emrakul isnt quite as toweringly powerful as, say, Emrakul, the Aeons Torn or Emrakul, the Promised End, it is still an Emraku