Going back to your original prompt...
I know that you bounced off of Dungeon World pretty hard, but I would say that Jeremy Strandberg's Homebrew World qualifies. It's a modified version of Dungeon World designed for one-shots, short campaigns, and convention play. It only exists in pdfs, as it is more of a fan project, which means that one can't just pick it up at a brick-and-mortar and run it.
Index Card RPG. It's super easy to read through and run. For anyone who thinks that D&D is great for "casual" play, then ICRPG takes the cake and beats it at its own game. Lay down illustrated index cards for your terrain like a board game or print out its art for monsters. It's designed for quick, easy play. With simple distances like close, near (or banana), and far. Character creation is a snap. As loot provides bonuses and HP is measured in hearts, it's super intuitive for people coming from video games too. It also has one of the better game mastery sections I have read.