Considering running a super-light, possibly GM-less (though I'll narrate and somewhat keep things on-rails) game w/ a horror/Cthulhu theme.

I'm familiar with Ghost/Echo and a few other such "one-shot" super-light systems, but I'm also open to suggestions.

I'd love a game of Ghost/Echo, or maybe Cthulhu Dark.  I've run both before, but haven't managed to play either.  What sort of scenario did you have in mind?

Don't know exactly. I'm aiming for a GMless system, so the dice determine when PCs die, but as GM, I'll let players make new PCs posthaste, to keep the story going, more or less.

As for story/plot, I figured I'd offer a little guidance and let the players narrate a bit more, since Ghost/Echo is GMless. I have an idea to patch in a little Dread-esque PC death into the rules, so all I'd have to do is ajudicate rolls and more or less keep the narrative in line.

Something Cthulhu might be cool, or a series of scenarios, as PCs die in one IC thread, they move to a new thread. One's a slasher, another some kind of alien monster. The possibilities are endless. Players can propose new ones, or revisit old ones with new characters (who doesn't love a sequel, right?).

Long term, I'm trying to find a system/game structure that's proof against the failings of PbP. Failing to post, players waiting on one another, all that stuff bogs down a game. Keeping things lively and interesting should be the only big challenge. I figure this sets all the complex rulesets aside and will let players (myself included) just have fun with the scenarios and writing.