I bought Zelda TP, Excite Truck, and Rayman. Zelda is of course a must have, as it's another excellent Zelda title (possibly the best one, but I think it's tied with OoT, given it's many positives, but those very few negatives, where I prefered OoT). I can't wait for the next Zelda title
Excite Truck is pretty fun, but you have to be able to get used to the sensitive controls, mainly how your truck steers. I wouldn't call it a "must have" title, but it's fun enough to justify the purchase to me
Rayman is pretty fun as well. The biggest downside to this game is that you must unlock the mini games in singler player mode before you're allowed to play them in multiplayer. The dance mini games seem like they will open a door for a "Drum Hero" style game, which I really hope somebody does make one. Just like Excite Truck, I wouldn't call it a must have, but it's a fun game. I wouldn't buy it if your brother won't be playing multiplayer with friends/family
A Wii Points card might not be a bad idea, either. I got one of those for my birthday, and I was happy to receive it as a gift. I had already spent 500 points (out of the 1,000 that I bought myself) on The Legend of Zelda (wanted to play it again, but I didn't feel like hooking up my NES) and was pleased with how nice the emulation was. There are promising titles that will be released in 2007, and I bet a lot more good games that haven't been confirmed yet will be, too