Another recent game purchase has been ACTION CASTLE! and JUNGLE ADVENTURE, using Jared Sorensen's Parsely system.
These aren't really role-playing games in any normal sense. They're based on 1980s text adventure computer games, with one player as the parser (and the map and descriptions of everything), and everyone else as the person typing in commands. Each player takes it in turn to type in a single command.
I played in ACTION CASTLE! at Kapcon, and enjoyed it so much that I picked both it and JUNGLE ADVENTURE up last month.
Running the games as parser is at least as much fun as being on the other side (you get the fun of knowing what they should be doing, which is usually not obvious to the others). I've run both games at lunch hours at work for a few interested colleagues, and that was a fantastic venue for it. Silly, and short, the games were a lot of fun.
Recommended when you need a short, silly game for any number of people (my experience suggests that the more people playing, the better).
ACTION CASTLE! doesn't have much room for replay - once solved, it is pretty much done. JUNGLE ADVENTURE is a bit longer and much tougher. My colleagues managed just 50/100 points when they finished, and there are more variations available. I suspect that you could happily play this 2-4 times before you discovered everything.