Jesus, did you just suggest GUN for a 10 year old? NO. That game is one of the most violent, brutal, sexual games I have played in a long time. It also happened to be one of my favorites, but that does not change the fact that it is not for a 10 year old.
I would suggest
Need For Speed Carbon
Halo
Call of Duty
At 10 years old, it is hard to find a game that is not only appropriate for them, but is also engrossing enough and fast paced enough to keep them focused.
Although, if content is not an issue, there are plenty of games the kids will want to play just based on the name.
Counterstrike Source
Gun
Gta: San Andreas
Hope I was able to help.
Dex