vetetris is a game written in Java. It's similar to tetris, but it is played in 3D. There are figures which are falling that have to be placed in the right manner. You can rotate the blocks in six different directions and move them in five directions. As time goes on they move faster and faster, and it gets harder to put them in the right spot.
viztool generates diagrams of collections of Java classes. It presently has only two visualizations: one shows inheritance hierarchies, interfaces implemented and inner classes declared, the other, a more detailed view of the classes, including public fields and methods. It is structured to allow the implementation of other visualizations. It uses the Java 2D API for rendering, but does so with the expectation that the diagrams will be printed, rather than rendered to the screen (though screen rendering is supported).
vxref provides integration of the xref tool into vim. The xref tool is a cross referencing and refactoring tool with a free version available that parses C and Java code, and a paid version that parses C++. vxref brings solid auto-completion (as opposed to all sorts of flakey varieties such as omni-complete) and accurate code browsing with scope information to vim.