This was a couple years ago. I wanted to gain experience in making games before I left school. I knew a couple guys who were interested in working in the game industry so I got them together to make a game. (more specifically to come up with a pipeline for game production: the game being a byproduct.)
Early In the process we had 3 of these idea pitch sessions to get a feel for what type of games everyone was interested in. This is the 3rd and final session before deciding on the way forward. We throw out ideas for racing games, shooters, puzzle, and horror games.