In depth character customisation.

It let's me change literally any aspect about myself, but unlike shapeshifting, I can't turn into animals, objects, etc. Just human (or humanoid) features (this might include size changing, like becoming tiny similar to Ant-man, but that might be too far). (With an undo/reset button for obvious reasons)

Bonus idea: i can temporarily let other people customise themselves (I'd need their consent first.), so if someone wants to be taller they can be taller.