Research and Development is a puzzle-centric mod for Half-Life 2: Episode Two featuring an unarmed player but plenty of violent mayhem.
The first time I saw this mod I wasn't very interested but it turned out to be fantastic. The mapping was great, the puzzles were amazing, there were subtle bits of humor in there, and I was having tons of fun playing it. This is a unique mod experience that nobody should miss out on. You get a well deserved 10.