Cthulhu Dark -Free two-page edition
Cthulhu Dark is a rules-light system for Lovecraft roleplaying. It's freely available from my website. If you order from here¸ you're rewarding me for the work I've done in developing the game¸ and thank you very much.
The rules are fun and incredibly minimal: they fit on one sheet of paper. You don't need a character sheet to play¸ so you can start playing after two minutes of prep.
Despite the simplicity¸ it's an effective and elegant system¸ with some surprising twists in the rules. You'll need to play them to get the full effect.