Woodman's Immaculate Maple Syrup Studio
Automatically makes your pictures more pleasing. Is both a standalone app and a plugin for Apple's Photos app.
Send Midi commands (CC's ...) to several keys/synths at once with 1 push of a button. Buttons can also be triggered by incoming MIDI commands.
Buttons or received MIDI commands can also start visuals (movies or pictures/slideshow).
Audio compressor app : is both a standalone app with IAA (Inter App Audio) support and an AUv3 audio unit plugin.