Cupuaçú and graviola, both Amazonian fruits, both a bit expensive in Rio, neither tasted all that great. (I am sure they taste better when you get them fresh up north where they come from.)
An some caipirinhas made with local “frutas de estação” (seasonal fruits):
Clockwise from upper-left to right: kiwi, passion fruit, kiwi+strawberry, pineapple, passion fruit, strawberry, passion fruit. Strawberry and kiwi make decent caipirinhas, but you have to make sure to first cut the fruit, then mush it well.