The first video game based on the manga came out last summer. Hayate no Gotoku! Ojousama Produce Daisakusen Boku Iro ni Somare! just recently released, though, and comes in two different versions. The main difference in the two versions is the setting, as one takes place at a rich girl named Nagi's school, while the other takes place at her mansion home.
The game has a Pygmalion/My Fair Lady type of storyline, in which the butler of the house must train Nagi for an Ojousama (lady) contest. You control Hayate the teen butler, and must pick out Nagi's clothes, scout out her opponents, and take her out on dates (to relieve her stress, of course). Ultimately, your goal is to make the bond between Hayate and Nagi as strong as possible.
We're going to bet that this shows up in the Japanese sales charts sometime soon -- any takers? Also, if you're interested, you can check past the break to see the boxarts and some screens.