神秘果 Miracle Fruit
There is apparently a fruit grown in China (including Hainan), not necessarily to be eaten, that has some very interesting properties. If you eat it, it tastes like a second-rate cranberry. It is not eaten for itself, but eaten because of what it will do to the taste of other things. If you chew on it in your mouth for a minute, the flavours of everything else will change for the next hour or so.
Balsamic Vinegar will taste like apple juice. Grapefruits will taste like candy. Brussel sprouts will taste like fruit with an extremely odd texture. The list goes on.
Next time I am in China, I will have to try it out… or I could buy it online at some expense.