GM_Agglutinaatio by Miigga is a small single player map. It's puzzle oriented, so if you want to play it through, you'll need to get your thinker going.
In addition to being a nice small single player campaign (even though there's not much story) it's also good for posing comics in, and even making a small movie in.
Oh, and the map maker says there's a secret hidden at the end of the map. See if you can find it!
Download it here:
If you need more information or help with this map, check out its forum thread.[...]