Just an idea I had kicking around that I'll throw out to see if anyone bites. I suppose I'm probably robbing bits of Hellboy and the BPRD, Supernatural, Buffy/Angel and a bit of CSI, in a rather World of Darkness setting. The ideal tone would be that blend darkly humorous and disturbingly dark.
The Premise: Virtually every supernatural creature one could care to name does exist, though the vast majority of humanity is oblivious to this fact. Some, like the Fae, just want nothing to do with the modern world, the smoke and steel poisoning most of them. Others, like werewolves and vampires, blend into the great seething hive of humans, carrying on their own agendas. Not all humans are oblivious, and plenty of them are gifted in their own right, either with the intelligence and strength of will to accept the truth and confront it or, more rarely, with bizarre abilities that could be called psi, magic or whatever name that happens to fit.
Something is upsetting the delicate balance though, and supernatural creatures are becoming more and more brave. New crimes are leaving conventional law enforcement authorities useless, as ghosts don't leave fingerprints and there isn't a dog in the world insane enough to track down a werewolf. The obvious solution is to set a monster to catch a monster. To this end the higher authorities have authorised the recruitment and training of a team of supernatural law enforcement officers, capable of meeting the otherworldly criminals on their own terms.
The Characters: Most of the characters will be recruited primarily for their innate talents, followed by their experience and temperament. Some may be willingly working for the new unit, while others may be forced to do the job. The exact details are best left to the player. It may be possible that some of them have previous law enforcement training, or even an intimacy with the wrong side of the law.
The unit will require agents who can maintain some level of control, as well as pass for human in most circumstances. Given that they'll have to work with purely human agencies, there is room for humans within the unit, working as a liason with the other agencies and reminding the monsters who is ultimately in charge.
Here's a rough example of the sort of team they'd be trying to build. This is just so folks can get an idea of just why anyone would bother hiring monsters in the first place. Obviously a larger team would be nice, and certainly more variety would be wonderful. Different bloodlines exist among each group of monsters, so there's no guarantee that even two vampires might be remotely similar in anatomy or abilities.
Vampire: Intelligent, charismatic and physically resilient, a vampire is ideal for getting past human security, being able to charm most anyone with a little effort and unable to be detected by electronic surveillance. Undead resilience, keen senses and superhuman agility and strength make for an excellent spy, sniper or brawler.
Werewolf: An unequalled sensory array coupled with several hundred pounds of killing machine makes for an ideal shock trooper and forensic analyst. While not so subtle as the others, there are times when there won't be any perpetrators left alive to tell anyone about the eight foot tall death beast they saw.
Human: While not gifted with supernatural powers, any human element of the team will have the advantage of being utterly mundane. Salt, silver, sigils, seals and all manner of supernatural defenses have virtually no effect on the average human. It may not seem like much, but human adaptability is the reason they've managed to crowd out almost every species, even the ones capable of benchpressing cars.
Psychic: While technically a human, a psychic is so far removed from true humanity that they are most definitely classified as monsters. The exact abilities and methodology varies from person to person, some calling themselves wizards and performing elaborate rituals, others considering themselves psychokineticists and wielding mental force on an instinctive level. Needless to say, skills such as psychometry and telepathy make for a detective like no other.
The Character Sheet:
Age: The character's apparent age, not their chronological age.
Birth Date: Day/Month/Year. This can be important for those things that don't have human lifespans.
Nationality: Your character's country of birth.
Distinguishing Characteristics: Physical or psychological.