This probably sounds like a complicated way of making random-sounding bursts of sound, but in practice I have found it very useful for creating pleasing rhytmical patterns and melodies. The interface makes it very easy to drastically change the rhytmical quality of a sequence, unlike in a traditional sequencer.
Of course, it's also fully capable of creating crazy and uncohesive patterns if that's your thing

You can have 1-6 balls bouncing around in the rectangle at any time, each ball has it's own horisontal parameter strip, and an associated color.

Price: Free
Difficulty: medium CPU: medium