My local newspaper publishes a puzzle called "The Challenger" (where you guess what numbers in a 4 x 4 grid will add up to the totals at the end of each row and column). It frustrated me because there's no one right answer -- you were just supposed to start guessing numbers until you stumbled onto a sequence that worked.

So I wrote a nice elegant program that crunched through every possibility (using 12 nested loops), eventually spitting out solution after solution after solution. The first time it produced a valid solution, I was thrilled -- and from then on I felt like I'd already somehow solved all the puzzles in advance.