Kaffeine is a media player for KDE based on VLC, which gives it a wide variety of supported media types and lets Kaffeine access CDs, DVDs, and network streams easily. Kaffeine also has an excellent support of digital TV (DVB).

PNMixer is a simple mixer application designed to run in your system tray. It integrates nicely into desktop environments that don't have a panel that supports applets and therefore can't run a mixer applet. In particular it's been used quite a lot with fbpanel and tint2, but should run fine in any system tray.

gElemental is a GTK+ periodic table viewer that provides detailed information about chemical elements.

ResidualVM is a cross-platform 3D game interpreter which allows you to play LucasArts' Lua-based 3D adventures (provided you already have their data files):

GNOME Secure shell Tunnel Manager is a front-end to manage secure shell tunneled port redirects. A port redirect is when you use secure shell to tunnel from your machine through another machine.

Play it slowly is a piece of software to play back audio files at a different speed or pitch. It also allows you to loop over a certain part of a file.