Horror/Suspense RPG heavily relying on actual role play, but utilizing the dice pool system to determine outcome of specific actions and combat. It's an older game but one that my players and I have been really enjoying because it's so different that what we've been playing.
World of Darkness is a simple system to pick up and learn. It only uses a d10 and has so much room for growth throughout your story with the expansion books. Even without them, your imagination is your only limit.