My favorite thing to add to beer is honey. You need to be a little bit careful though, like someone else said. For most beers, especially med to low gravity, you should use honey as 20% or lower of your total fermentables. If you get into the 1.060's or 1.070's I would say you could go up to 30%. In my experience anything above that give too dry of a taste and takes longer to age out. You have to play with it to see what you like, but that is my advice. Good Luck!