Trackbout has launched Ripchord, a free MIDI plugin designed to be obnoxiously simple for creating and remixing chord progressions.
It lets you map multiple output notes to a given input note so that you can create your own custom chord mappings, and then experiment with the order and the rhythm of the chords by simply playing one note at time.
Ripchord is free and will always be free, and you can also download free presets from the community.
Ripchord is available for Windows and Mac in VST/VST3 and AU plugin formats.