Simple 3D graphics project?

I'm looking for some good ideas for a simple 3d graphics program as my final project for an intro to computer graphics class. As for some background information, we'll be using opengl and will have a little over a month to work on it, so nothing too far-fetched. The simpler and "prettier" looking, the better. It does, however, require some sort of interface that the user can interact with (so a very simple game or similar is a good idea) and must be 3D.

My only idea so far is maybe a 3D version of Tetris (google for some examples).

Edit: I ended up going with 3D Tetris. For a less than a month's worth of time, you can see what I came up with here.

A 3D text/code editor. Text is 3D, errors stand out, code indentations not only indent, but protrude on z axis, pages/files are 3D and can be flipped like a ringpad.

Probably not useful, but fun and more interesting than a game IMO.