Here's the rundown for my dark fantasy/horror campaign:
NUDITY IN MY GAMES: Yep, when its appropriate. Slaves are often sold nude so buyers can see the general health of the slave. Prinsoners are stripped, etc.
NUDITY IN MY BOOKS: Doesn't bother me at all- although art done solely for the cheesecake/beefcake purpose is too much and over the top. Demons/primitives/etc nudity doesn't bother me though.
SEX IN MY GAMES: Flirting is fine to role-play through, but everything past that is off-screen. I have seen this one abused in another DMs game when I was younger, and I vowed NEVER to role-play through it at the table. When I do solos with my girlfriend however....
SEX IN MY BOOKS: I'd prefer not to have this in the books- we all have imaginations after all.
NECROPHILIA: Yes, it has come up twice- in neither case did the act occur where the PCs could witness it- thats too much. Once was a former noble turned ghoul by his tastes for human flesh. He made his mistress a ghoul, and continued "relations" with her after her death. The other was a very deranged elf assassin who hated humans and would defile their bodies after killing them. (Sorry if that is too graphic- I tried to keep it as tasteful as possible). In both cases, the added horror of necrophilia disgusted the PCs, and really motivated them.
BESTIALITY: Not specifically used- although a sect of barbaric, animal worshipping priests are believed to do this.
INTER-SPECIES SEX: I only use human PCs, and my world is human dominated, so it doesn't crop up too often. It is implied with the rare half-orc and half-ogre though.
VIOLENCE: Yep, I generally leave out really gory descriptions except in the case of horrific wounds, devoured bodies, or infernally-tied killings (sacrifice, etc).
TORTURE: Yes. Usually occurs offstage, although once when a PC was captured, the player wanted to play through his paladin's torture. I was reluctant at first, but after his compelling role-playing and faith to his god during the event, a slave who was moved by his faith and witnessed the torture helped the paladin to escape. In this case it added a lot to the story, but in most cases I leave it offstage.
MUTILATION: Almost always offstage. During combat some mutilations occur, such as the NPC cleric losing several fingers to an axe-blow.
CHILD MOLESTATION/ABUSE: I ALWAYS ask at the beginning of a campaign what the players are ok with in the game, and I specifically mention this one. I have used it in games- once with a deranged child who engaged in evil acts due to supernatural influence. His father, hoping to purge the evil desires from him had him placed in an oubliette. In another case, a cthulhu-esque entity mindlinked with many children and used them to further its plans. It incited the children into a frenzy by inflicting minor wounds on them, then sent them at the PCs. I never depict child abuse onstage though.
INCEST/RAPE: Yes, although implied and always offstage. I have found this is the topic most people are the most uncomfortable with, and I would be very uncomfortable depicting it during play. It is the ultimate act of degradation, malice, and showing domination over another person.
MENTAL ILLNESS: Yep, all the time. I have degrees in psychology and biology, so I try to portray mental illness as accurately as I know how. Honestly, mental illness fits in with many of the deviant behaviors listed above, and often is a motivating factor. It makes a villian more compelling than just an "eeeevil" factor.
INFERNAL/OCCULT MATTER: Yes, I use this a lot. Demons/devils figure prominantly in the cosmology of my world, and they are insidious, with cults popping up fairly frequently. I have found it most effective to hint at their practices/behavior rather than direct confrontation- the players make up far worse stuff on their own than I could invent.
In general, no subject is taboo from my game unless it REALLY makes one of the players uncomfortable. So far, nobody has complained, and I am lucky enough to have a very mature group of players. The extra depth added to the game by these topics makes the game more compelling for us, and more personally involving than a game that follows the comic book code.