VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
PiP for Mac - Always on top window preview similar to the popular windows only OnTopReplica
AIMP - AIMP : Free Audio Player : Официальный сайт программы
Helium - Helium lets you accept payments by credit card for anything you want to sell online.
foobar2000 - An advanced freeware audio player for the Windows platform.
X-Mouse Button Control - XMouse Button Control (XMBC) allows you to create application and window specific profiles.