A very good use for Auto-tune is to accurate record your own vocals for melody purposes for not for actual singing on the track. Many people like to hum a melody and then lay down a track later, starting with their favorite instrument. however if you are rather tone deaf, playing back your humming won’t help you at all. A good thing to do is either hum through Auto-Tune real time, or add an Auto-Tune effect to you humming afterwards. Either way to will get an accurate note snapped melody with with you can use for your productions.
I suggest you use to Auto-Tuned melody as a back bone of your track and lay other instruments over it. Once done then simple remove the humming.
Also remember that with Auto-Tune you can chose the scale and omit certain notes if needed. This function helps greatly if you are sticking to the one scale.
Auto-Tune isn’t just for fixing peoples off pitches, it can be a very useful tool if used correctly. Just make sure that you don’t rely on it for polished vocals.