1) Appear to the WBC, declare myself to be Jesus, and tell them they're all going to Hell.
2) Torment primary school/high school bullies until they either end as gibbering wrecks, or pale shadows of their former selves.
3) Turn Boris Johnson into a superhero. Just 'cause.
4) Possess a statue and pretend to be a Weeping Angel.
5) Choose someone I REALLY hate, possess anyone they come into contact with, and make them think that the entire world has gone mad/turned against them. Repeat until there is no-one left that I hate.
6) Take control of "celebrities" that do not deserve celebrity status (E.g. People who are famous just for being famous), force them to say/do stuff that makes them look like complete monsters, and leave them to the angry mobs with torches and pitchforks.
7) Make the world a much more fair place e.g. take money from privelleged, inconsiderate douchebags and give it to people that need it, spare innocent people from the wrath of evil companies with armies of lawyers, etc.
8) Use any means necessary to build a fighting machine from War of the Worlds, and stage a Martian invasion of Earth.
9) Possess a cat. I've always wondered how they work...
10+) (Insert generic ghost stuff here)