My DH's favorite flavor is vanilla and I can't think of anything more boring, so I'm always mixing stuff in. I like low sugar strawberry jam, granola, peanut butter and choc chips, and sometimes crushed up cereal like Cookie Crisp.
Another thing that's good is crushed pecans, brown sugar, a little flour and some butter. Cook in a pan and let cool. Makes a praline topping in no time that's very good!