I got a new gadget in the mail today: a Keyer Quick-Clip tuner. It's an interesting concept that uses a little magnet to attach a small tuner to the back of a standard (and commonly used) Kyser Quick-Change capo.
Advantages: Since the tuner is on the capo, and a lot of people already clamp a Kyser to their headstock, it's one less thing clip onto your guitar. I also like that the tuner attaches/detaches easily. Maybe I'll just keep the tuner in my pocket and quickly (magnetically) snap it on when needed.
Disadvantages: You have to use a Kyser capo, although begrudgingly I already sometimes use one (rather than my preferred Elliott/McKinney or Shubb Finetune capos) when gigging, for faster changes.
Someone needs to hack an Elliott or Shubb Fine Tune so that a small tuner can attach magnetically to the back of their respective adjustment knobs.
Update: Here's a similar idea...a tuner that magnetically sticks to the back of a metal tuning machine. This as also an interesting concept, although (a) the tuner doesn't look as good as others and (b) it doesn't look like it would work for open-geared tuners like Waverlys.
BTW, my favorite tuner is the TC Polytune Clip, although I'd like it even better if it artculated in two dimensions rather than just one.
I also like the D'Addario NS Micro Tuner due to its small size and that it can be (relatively unobstrusively) clipped to the back of a headstock. They are also inexpensive (~$12 each, or ~$17 for a 2-pack), so I don't worry about losing/breaking them. Although it's wasteful, I almost think of them as disposable.