Courier Bat

The gate is the whole design: the recursion only fires if you gained life this turn, so the card is built to reward a deck that is already leaking incidental lifegain rather than one that has to stretch to enable it. That conditional is what keeps a flying 2/2 with a Raise Dead stapled on from being oppressive. Read the trigger carefully and the payoff is smaller than it looks: it returns a creature card to your hand, not to the battlefield, so you still pay the mana and the tempo to recast whatever you pulled back. What it does offer is a body that blocks and pressures in the air while quietly restocking your hand with the best creature in the yard, and it does that at instant speed only insofar as you can flicker or reanimate it (the trigger itself keys off entering, so blink effects turn the bat into a repeatable retrieval engine as long as the lifegain condition stays satisfied). This is the kind of small-ball value creature that lives or dies on the density of lifegain around it: pair it with a steady drip of incidental gain and the graveyard toolbox opens up; run it in a deck with no lifegain and the ability simply never triggers.