Peanut butter tastes good with lots of things. But someone I knew (I forget who) used to eat peanut butter and tuna sandwiches. The idea of the combination, let alone the smell of the two mixed together, was kind of nauseating.
Things peanut butter goes with:
jelly/jam, preferably strawberry
nutella
marshmallows/fluff
chocolate
fruit, especially apples and bananas
celery and raisins (ants on a log!)
crackers and various bread types
ice cream and milkshakes
and, according to Misconception, pickles, but I severely doubt this combination