According to ESRB, this game contains: Animated Blood & Gore, Animated Violence, Strong Language
I hope I don't need to tell any parents reading this that they should do everything possible to keep this game away from their kids. The problem is that parents are going to have to be extremely diligent because not only is the game made to appeal to the young, but also the uncensored demo is readily downloadable off the Internet. Kingpin is basically what-you-see-is-what-get, offering virtually nothing below the surface.
Hardcore FPS fans who don't mind the same old, same old in the gameplay department and appreciate this type of offending material will love this game. However, gamers who expect innovation in content as well as in gameplay won't find it here. If you haven't already, try Half-Life, Rainbow 6, Thief, or even Aliens Versus Predator instead.
As for mature gamers, don't fall for all the hype. The violence in Kingpin never goes beyond a childish gee-whiz mentality that not only pushes for the lowest common denominator, but also revels in it.