I hate "puzzle" questions where there's a single insight with which the problem becomes trivial, without which the problem is unsolvable, and it's a tossup whether or not you'll come across it in the 30-60 minutes you spend in a room with the interviewer.
I do enjoy questions where there the path to the goal isn't immediately obvious, but there are immediately a couple of approaches to consider, and even though the problem itself might be novel, the steps to get there are each something a competent person can reason about.
I do enjoy questions where there the path to the goal isn't immediately obvious, but there are immediately a couple of approaches to consider, and even though the problem itself might be novel, the steps to get there are each something a competent person can reason about.