I’ve done a couple
All Magical Swordfighters - everyone was a late teens student at an academy based in Cardiff in the year 1636 ER (the Era of Ravens, so named for the Morrigan’s act 1636 years ago of bringing failing magic back into the world by making demigod children with Mordred ap Uther after helping him defeat his half brother) it is a world of Empires in a tenuous peace, and the Academy of Ddraig Goch is part of keeping that peace by bringing in students from across the known world.
The PCs are all memebers of a “Chimneys” team, which is a sort of parkour rugby game.
All Monsters - Every PC was some kind of classically “monstrous” race, dealing with a world ruled by the “pretty races”.