This game definitely deserves it's M rating, but doesn't hold a candel to others like Grand Theft Auto.
Violence- there are spurts of blood when you or enemies are hit, but there's not a fountain. When a character is killed, a puddle of blood sometimes grows around thier bodies. Your character can be decapitated by a chainsaw, but it's off-screen. Sometimes zombies' heads can be shot off, and the parasite briefly gapes from the open neck wound. Several people are infected with a parasite that overtakes their bodies and covers them in a swarm of worm-like things. People (zombies included) are impaled, crushed and sliced. Every character has a set of physical attacks, which range from a crushing punch to the face, impalemant with a knife, and snapping necks with bare hands. There is one game mode where the player kills as many zombies as he can as quickly as he can.
Language- The language is pretty heavy, but better than most R-rated films out there. There is one f-bomb in story mode, and another on the Gold Edition. There are four or five uses of sh*t, the same number of d*mn, a few uses of God as exclamations, and about one use of b*stard.
Sex- There aren't any sexual situations. Sheva wears tight, cleavage-revealing clothing, and several of her unlockable costumes are little more than a bikini. One female character wears a dress that cuts to her stomach and lower back. There is one scene where a character uses slight innuendo.
Attitude- Obviously the bad guys have pretty a pretty bad attitude for trying to bring about a sort of apocalypse. Chris and Sheva risk their lives to complete their mission, protect/aid fellow agents, and to rescue Chris's friend. At one point Sheva almost backs out, but decides to help Chris stop the plan to infect the entire world with mutating, sometimes fatal parasite.
Other concerns- there is controversy over this game and where it takes place, but I don't see why it's racist. They're in a poverty-ridden area of Africa, so most of the population will be black. Sheva is black, so why is there such an uproar over a white man killing black zombies in self-defence?