Bad areas and unlikely locales . . .
Systemless Tales - These Tales of Terror
are completely systemless and can be dropped into any roleplaying game with barely any adaptation...
Call of Cthulhu - These Tales of Terror have been written wholly or partly with Chaosium's Call of Cthulhu roleplaying game in mind. (But frankly, you can drop them into most other games.)
The following Tales of Terror heavily involve the Cthulhu Mythos.