I recently got my hands on Liquid Music by WaveDNA. It's an awesome plug-in or Max for Live device that allows you to draw in melodies and chords. It's as simple as waving a paint brush across the piano roll. I think it's really cool for coming up with unusual ideas and new workflows.
Read my full review and watch the demo video on Ask.Audio.
Liquid Music is currently on sale until August 31st.