John Galt said:
Dirty thirties would allow for a Valentines Day Massacre lynch of some sorts and a whole mess of hooliganry. Bioshock would give us a lovely setting and but the plasmids would be impractical to manage in an RP. It's been suggested that we do a KotOR-themed one but again, you've got plenty of people with magical powers floatin' around.
I've never played KotOr but I know my Star Wars. That could be pretty good. But like Saskwach said, no Jedi's because they could easily read the killers mind. Unless the killer was Sith! Dun dun dun! Oh, I just gave it away. I guess we could have a group of all intern Jedi's if that's the case.
I like the Bioshock idea. It should be set pre-chaotic destruction. Maybe the time when plasmids were in the air and all was fine bar a few minor phycho's tearing people to pieces. Perhaps the killer was a smuggler working for Fontain? If we do the Bioshock one it would make it easier if the building was cut off from the rest of Rapture via leak of something so there's no escape.
The gritty 30's noir would be very nice as well. If so, shotgun mob stooge... no wait, journalist trying to get the scoop... no wait, prviate eye detective. So many nice choices.