Something I have always thought of was the power of smoke-manipulation. The power of this ability could range for a mediocre character to a very serious threat, but there can be many applications for the ability to control or generate smoke. The obvious one is creating a smoke-screen, limiting vision and making it difficult to breathe for any enemies. You could also use smoke to deliberately blind or choke a person, make signals/shapes, or just make people high. Some of the high-end powers I have thought up include teleportation and item generation. The teleport is rather restricted, if you see a column of smoke from your current position, you could evaporate into a cloud of smoke and appear from the column seen earlier. Item generation goes in the way that you would be able to craft something out of smoke, and it takes a semi-solid form. Think of robes or armor made out of smoke, that swirl and look all mysterious, or dual swords that leave smoke trails when swung.