Treebeard, Gracious Host can grow quite large in a hurry with the right amount of lifegain
Even though it's now treated as a "holding zone," it's still often seen as being gone forever
Even three lands sacrificed make this a 9/9, allowing you to dig 9 cards to replace those lands
That means that we'll exclude cantrips from this ranking, cantrips being the MTG slang term for cards that draw you exactly one card in addition to other effects you may hear players saying cantrips replace themselves because you play them and you get a new card in your hand
A bit more mundane than the scores of horrors and demons we've just gone through in both Black and Blue, but I do like the idea of a giant grinning snake-hallucination with hands tormenting someone and screwing over their head
At the very least, building this into your own deck can ensure that youre always untapped and ready to go