XMMS Telnet Remote
Back in the day I had a separate server with all my MP3 files that was always on and hooked up to my audio system, and I mostly used a laptop to access it. I grew tired of using VNC to change the music, so I created a Windows application that could telnet into my server on a port where XMMS was listening and change the song, effectively making it as simple as though I was running XMMS on my laptop.