There are few of these but they are all common: Blood Runs Chill (8R3) , Galadriel, Lady Redeemed (10R11) , Roll of Thunder (4U99) , Arrow-slits (5U80) , and Derufin (7R87)
I understand that you need to run four colors to pull this off, and Im not sure if Standard has either the manabase or the cantrips to try to move in on that approach, but Modern should easily have all the necessary tools available (not really considering it for Legacy as combo decks have a much higher bar to climb there, what with Tendrils of Agony and Show and Tell alive and kicking)
You can tell the top-down design here, where someone asked: If I design a card to be a moat, what would it look like? It might not be the most powerful, especially when decks dont necessarily need to attack to win, but its still cool and combines well with cards that enable flying
Planeswalker - Repeatable Spells on Legs A planeswalker enters with loyalty counters