i would still say diablo 3. no clue why a tool wasnt brought out for this. then i also hate that when people asked the thread was closed and a mod put a link to another site that uses another tool. that made no sense to me.
Skyrim would be a good one because there so many things you can do with it like add new weapons and armor new quests new characters new spells and shouts that would be awesome or just a unstoppable character of destruction or you can edit the power of your weapons and magic or give your character items like they did for oblivion