Here's a bit of a food-related brain teaser that I read on a different forum. Take three foods, we'll call them A, B and C. Liquids will work as well. The combinations of any two of these items (A+B, A+C, B+C) would be perfectly edible and in fact might be quite good, even if something you personally might not like. All three of the foods together, however, would be disgusting.
One example involved tomatoes, cream and lemon juice: tomatoes + cream = cream of tomato soup; tomatoes + lemon juice = salad ingredients; cream + lemon juice = curdled cream, not generally eaten on its own but a base for making custard; tomatoes + cream + lemon juice = blecch!