Turbo Tuner - I'm a huge fan of this pedal:
I own one of each. The pedal version is very steady, very accurate and precise, built like a tank and acquires the note very fast. I like it better than the Peterson pedal tuners and yet it's only $129. I hope more people buy them so they stay in business.
When you try them side by side, you'll notice that your guitar sounds better when tuned with a Turbo or Peterson. However, Petersons had a lot of failures in the past, so I chose this. It's been rock steady reliable. And small.