Rebound. Essentially, Rebound copies a spell, giving you it once when you cast it for its mana cost and again at the beginning of your upkeep for no cost.There were only two cards that utilized that mechanic at Common, and they were both excellent: Staggershock and Distortion Strike. Staggershock was typically a two-for-one given the fact that most Common creatures have two or less Toughness. And Distortion Strike fueled several back-breaking combos, including dealing unblockable Poison damage to your opponent two rounds in a row.
Here's the text from the Comprehensive Rules on Rebound, for those of you who go for such things:
So far, only one Common with Rebound has been spoiled for Dragons of Tarkir:
Rise of Eagles, which for one mana extra creates both tokens right away and gives you Scry 1 in addition. Since it's a Sorcery and not an Instant, your opponent will in fact get a whole turn before you receive the second 2/2 flying token. That said, being able to cast it a whole turn earlier is a noticeable upgrade, since even in a dedicated Control archetype there can be a big gap between having access to 5 and 6 mana. Right now both Izzet and MonoU Control lists are running Rise of Eagles, and since the latter lacks access to the similar Flurry of Horns, Ojutai's Summons would probably slot into that deck pretty well.
Given the potential for on-board two-for-ones from Rebound, I am not optimistic that we will see more than a couple of these at Common, and possibly only one. Or maybe we'll get lucky and Staggershock will get reprinted at Common. Time will tell.