I'm not sure why, but I've been perpetually obsessed with head stock tuners, and tuners in general. Here's my personal findings on head stock tuners.
Snark: I wanted to hate this thing, but the original modes seemed accurate and were VERY fast. They are just super ugly and tend to break after a year or so. This is fine because they are $10 or less.
Planet Waves/D'Addario: I want to like this because it's so small. I have a couple and they easily fit in accessory bags and cases. I'm not happy with the response times or the accuracy. It always sounds a BIT out of tune. I do like that it can be left on and mostly invisible.
T.C. Polytune: I really like my Polytune iPhone app, but I can't bring myself to spend 40-50 on a head stock tuner. I've used the Polytune in stores, though. It's really nice.
Korg Pitchclip: Kind of hard to find, but quick response and good sound.
I've used a bunch of other clip tuners, but none worked any better than the four above. I've never tried the Peterson strobe clip on.
My favorite tuner is still my old Boss TU-12h, with an actual needle. The mic doesn't do so well in noisy environments, but the actual needle is so nice to read for accuracy.