Some things I have done with Melodyne other than fix vocals:
• A guitar sample did not sustain long enough on the last note of the song. I used the timing tool in Melodyne to stretch it out to sustain as long as the other instruments so I could do a smooth fade.
• After recording a guitar and having the note sustain for four beats, I realized it conflicted with another part, so I shortened it to two beats so it was gone before the chord change.
• Removed vibrato from a harmonica sample to make it sound like a melodica.