Here is Cube Quest, a game I programmed in Java for my 3D graphics class at BYU. I made a little video so there would be a record of the project outside the program itself.
Working in 3D adds quite a few things that a flat game can mostly ignore. The camera has a position and a view of its own, objects need to make sense from more than one angle, and depth becomes part of how the scene reads. The blocky world is a nice fit for a project where I want to concentrate on those pieces without spending the whole time making complicated models.
It is a class project rather than a giant game, but getting a world on the screen that I can actually move through is a pretty satisfying result. The demo is below.