Whenever you attack with one or more creatures, exile the top card of your library. You may play that card this turn. If it's a creature, Aura, or land card, put a token onto the battlefield that's a copy of it, except that if it's a creature, it has base power and toughness 1/1 and it arrives tapped and attacking. Sacrifice that token at the end of your next main phase.
See Challenge # 167: 6(2-4)-3-6-2-1
A blue-red mythic enchantment, CMC 2, that fits into an aggro deck? Oh boy.
Gosh. Yes, that's a tall order but that seems to be a good answer :)