mausezahn (mz) is a fast traffic generator written in C which allows you to send nearly every possible and impossible packet. It is mainly used to test VoIP or multicast networks but also for security audits to check whether your systems are hardened enough for specific attacks. Mausezahn can be used for example:

Navit is a car navigation system with routing engine.

aubio gathers a set of functions for audio signal segmentation and labelling. The library contains a phase vocoder, onset and pitch detection functions, a beat tracking algorithm and other sound processing utilities.

Flip your (or your "xhost +" using friend's) screen on either the vertical or horizontal axis or melt away the graphics on your display. Both commands, named xflip and meltdown, have a -planes option to independently act on individual bit planes. This version now comes with a new -oblic option which flips horizontally and vertically simultaneously.

Userinfo is a small console utility to display as much information about a local user as possible. It supports the output of password file info, home directory mode, mail info, lastlog info and more.