Hatogate
Hatoful Boyfriend is a game that really defies description - certainly if you want to avoid sounding completely insane in the process. On the surface it's a visual novel about going to a school full of pigeons, but it manages to raise the bar on lunacy from there multiple times before you reach the end.
I'm now part of a group of friends who have been doing a voiceover playthrough for it, and Xaq created this in tribute - I then took his script and worked it up into a Flash game. Writing a Shadowgate-alike was an interesting challenge, written about at great length here.