According to the ESRB description for The Elder Scrolls V: Skyrim, it will certainly live up to its newly assigned "M" rating. Not that this is a surprise, really, but we do have additional information as to just how far the game will go.
As players trek through the wilderness as Dovakin, who has the prophesied power to slay dragons with swords and spells, they will encounter battles that will go into slow-motion for "large blood-splatter effects" and decapitations, not unlike the V.A.T.S. close-ups in Bethesda's Fallout series. Several dungeons in particular will be adorned with "heads impaled on spikes" as well as "prisoners chained to a wall" as "they scream in pain amid splashes of blood or fire".
Dialogue will frequently have sexual material and will even be slurred in drinking contests:
As the game progresses, the dialogue and on-screen text contains references to sexual material (e.g., “. . . all the whores your heart, or any other organ, desires,” “She . . . raped the men as cruelly as Bal had ravished her,” and “Remember when you thought [he] was . . . intent on making you . . . into his personal sex slave?”). Alcohol such as wine, mead, and ale can be purchased and consumed by players' character throughout the game; and in one sequence, players can engage in a drinking contest with another character, which eventually results in slurred speech (e.g., “One more. No problemsh . . . Thash grape!”).