I used to get pretty crazy. Sometimes I'd do a peanut butter and Kit-Kat sammich, sometimes a peanut butter, chocolate chips and then added some powdered sugar, sometimes peanut butter and banana. Go crazy!
A little peanut butter goes a long way, but the jelly, the jelly you need to load up. Also, try putting crushed potato chips in there. Nice salty, crunchy kick.