DS2 was 6 today, and he got some great new games: They are really thought-provoking. Both of them can be played at a fairly simple level, but rapidly become more complex as you learn different strategies.
Tantrix is here
Blokus
They are both £20, which is a lot for a game, but they are good quality (feel nice), and anyway I didn't pay for them!
I just thought I'd recommend them in case anyone is looking for something "a bit different".