In college I wrote a little Sudoku solver for an algorithms class which was more or less brute-force with backtracking (and a little intelligence about which part was the weakest and should be brute-forced first). A fun exercise, but for better or worse, I don't play Sudoku anymore. I solved it; the slowest part of getting the computer to do it for me now is the data entry. I've lost all motivation to do it by hand.
I wrote an intelligent solver (doing set elimination, etc) in Java back in high school, but couldn't get it to solve the harder puzzles. Clearly I was lacking one of the essential implications that allow you solve them manually. I actually never even considered brute forcing it.
