Now that clip-on-headstock tuners are so cheap on ebay I think any other sort (apart from the horridly expensive strobe ones if you are paid megabucks to perorm) are history. They are very resistant to noise, and will also let you tune by plucking your own strings softly so you can tune quietly without leaving the session.

Intellitouch - expensive, many say better than the rest
Intelli - still quite dear and I find the LCD response a bit too slow
ENO 3000 - my preference, and really quite cheap
Joyo - stupidly cheap sometimes but I find less effective at recogising the note you are tuning.

All, I think, have a mic as well as a clip setting, which can be very useful if you have recorder players with you: quite a lot of recorders seem to be a smidgeon sharp (between 2 and 5 cents) and need the top joint pulling about a thumbnail to be in concert.