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.
Loopy Pro - Loopy, the sophisticated, tactile live looper app that reinvents iPhone and iPad music making.
G-Stomper Studio - G-Stomper Studio is a feature-packed, mobile music production tool.
Group the Loop - Live Looping with usefull GUI, Verse/Chorus layer system, drummer, effects, etc...
Caustic - Caustic is a music creation tool inspired by rack-mount synthesizers / samplers rigs.
Repetito - Repetito: the multichannel looper software for live performance on the PC.