FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
G-Stomper Studio - G-Stomper Studio is a feature-packed, mobile music production tool.
FamiStudio - FamiStudio is very simple music editor for the Nintendo Entertainment System or Famicom. It is designed to be easier to use than FamiTracker, but its feature set is also much more limited.
Caustic - Caustic is a music creation tool inspired by rack-mount synthesizers / samplers rigs.
MOTU Digital Performer - Get inspired, then refine your mix — all in a singular workflow.