Star Fruit

Pearlwood trees drop these occasionally when shaken, so it only exists once the world has gone Hardmode and the Hallow has spread somewhere with trees. Walking a hallowed forest and shaking everything you pass will turn up a few without any real detour, and the palm version on hallowed sand works the same way.

It gives the stronger of the two feeding buffs rather than the basic one, which puts it ahead of nearly everything else you find growing in the wild. The name trips people up: it has nothing to do with the fruit that raises your health, and it will not touch your mana pool at all. If you have Shimmer running, it is also one of the fruits that folds into the top tier food.