In quiet locations, such as at home, or in pawn shops, I prefer the free iPhone 5S Panotuner iPhone app, which is about as good as it gets for an acoustic tuner....but, as with all microphone-based tuners, it is useless in a noisy environment.

When you are playing in a noisy environment it can be tough to hear whether you've got the guitar tuned "just right"

You can tune your guitar in a noisy environment because it attached to the head of the fretboard and just does a great job of tuning making it super easy to always be in tune, works on both acoustic and electric and has a soft silk like feeling to it's coated exterior with nice soft rubber grips to protect the surface you're attaching to

With a clip-on Snark tuner, I can tune my 12-string guitar up quickly, even in a noisy environment