For me its:
- bananas that have lost their green: they get sort of dry and gucky and smell like acetone (nail polish remover). When they're still a little bit green they've got a really subtle, refreshing taste to them that isn't too sweet and their tecture isn't too mushy.
- okra: slimey + fuzzy - need I say more?
- the Royal Gala and Golden Delicious varieties of apples - they taste like straight up fructose
I'll think of more later...