Mastermind™ is a free advanced MasterMind clone with lots of different game variants, from the very easy up to really challenging ones.
You have 4/5 number guess way, 10/12 times to combine any color, but not pegs of the same color. ColorCode has also a rather intelligent ;-) built in MasterMind solver - so you can let the computer guess for you (nope, hes not cheating - really).
Enjoy!