Several of you might have heard of this excellent philosophical time waster before, but it’s new to me (apparently it was first devised by Wilfrid Sellars):
Identify three foods A, B, and C such that any two of these are complementary (taste good in combination) but the trio does not. So A and B must be complementary, B and C must be complementary, and A and C must be complementary, but A, B, and C must be foul when combined together. (It’s harder than I thought!)
Here are some possible answers. I opt for Coke, Merlot, and Chicken. The pointer is from Ananda Gupta.
Addendum: In the comments, Stephen Dubner nails it.