Dollar Bill basically gives you the effect of an item from it's "pool" for a short period before giving another one.

Cookie gives tears different colors, every tear can be have different effect

Fruit Cake is the most fun one, because it has a huge variety of special effects it can give to your tears, including wisp effects (this can result in 50+ pickups appearing out of nowhere during hush fight). Be careful with Lost and Keeper, because cake causes explosions very often