I use it on these (in order of preference #1 is best):
1) Home-made vanilla ice cream (this is one of my most requested items at parties),
2) Wheat toast,
3) Ritz crackers (I make it myself and save a bundle over the premade PB Ritz),
4) Chicken fried steak with mashed potatoes and gravy,
5) Celery.
I realize that #4 sounds awful.  But in school lunches, I sometimes was desperate.  I tried PB on the crappy chicken fried steak and it was very good.  But the school steak was dry and the PB didn't help.  One day some of my potatoes and gravy accidently got onto it.  I ate it and the moisture made it a perfect combo.  Everyone who was brave enough to try it loved it and ate them that way forever.  But, most people will be unwilling to ever try anything similar.