The Window is a freely downloadable, rules light roleplaying game developed by Scott Lininger in the 1990's.
A self described "simple, usable, and universal" system, The Window can be applied to any particular roleplaying genre. The original setting, The Stage, featured modern, supernatural, horror elements, but The Window has been run with fantasy and superhero settings as well.
The game play is heavily narrative/storytelling with dice (d4 through d30) used to determine tests of traits and applications of skills. Characters are defined by adjectives rather than numbers.
The rules can be read in about 5 minutes and the system applied to a given genre in another 10 minutes. Most of the background, skills, and target numbers for tests are made up by the storyteller and actors so not much more than pencil, paper, and some dice are needed to play.