XMPlay
A tiny Windows player from Un4seen Developments that became the tracker crowd's favourite because it played modules correctly — not just roughly correctly.
Ian Luck wrote XMPlay in the late 1990s, at the same small outfit that later produced the BASS audio library and the MO3 format. Where mainstream media players treated XM, IT and S3M as an odd afterthought, XMPlay made modules the main event: faithful handling of effect commands, a choice of interpolation, and the ability to mute individual channels.
The whole thing is a single executable of a few hundred kilobytes, skinnable and extensible with plugins for MP3, Ogg and nearly everything else. It never reached Winamp's mass market, but among tracker and chiptune people it was long the default answer to "what are you playing that in?".