According to ESRB, this game contains: Mild Language, Violence
Parents should be wary of this game-it's as violent, even for a First Person Shooter. The game is little more than an orgy of non-stop gunfire, and it more than earns its M rating.
FPS fans really need to run out and buy this game. If Half-Life 2 ever comes out, then maybe there'll be a better FPS out there, but until that point, this is as good as it gets.
Deaf and Hard of Hearing gamers should have no real trouble with the game. The only major thing you'll be missing out on is the dialogue, but it's neither vital to playing the game, nor is it particularly well-written.