Some of you may be interested in my latest attempt to bring Call of Cthulhu over to GURPS. Essentially, this is a setting guide for the 'Jazz Age' (actually I cover 1919-1939) with some new material for playing Cthulhu Mythos investigators using GURPS.
The major changes/features are a different way to look at Fright Checks/Sanity Rolls. My system breaks the Fright Check itself into two level of severity depending on the source: Stress Checks for 'normal' frights such as gory scenes, ghosts and other 'mundane' horror; and then the more mind-shattering Sanity Checks which are caused by insights into the true nature of the Cthulhu Mythos.
I also added a way to make increasing knowledge of the Cthulhu Mythos a mixed blessing. Knowledge of the skill Hidden Lore: Cthulhu Mythos
is essential to counter the machinations of the Mythos followers, but a successful roll will identify a Mythos encounter as being such, and thus potentially promote a Stress Check to a Sanity Check.
My main aim, however, was to give players a believable setting in which their 1920s investigators could operate. I am aiming for an immersive environment where characters react to the narrative as much as to the mechanics.
As always, comments and suggestions are welcome.