We know this isn't exactly high security, but if you have trouble remembering the combo for your gym or school locker, the $5.98 Wordlock from Staples could be the perfect solution. With only five rings, and just 10 letters per ring, it's limited to just 1,000 combinations, so it's certainly not hack-proof. But given that it's analog, anyone trying to do a dictionary attack will have to actually stand there with a dictionary (or, more likely, a generated list of all 1,000 combos) and try them all.
Update: Thanks to everyone who pointed out that there are 100,000 possible combos; we skipped the math and went with Staples' product description. That makes a dictionary attack a bit harder; looks like the old lock-cutter is the way to hack into this one.