I'd stay away from the Boss personally, I've had a few Boss pedals and found them all to have a negative effect on my tone when in bypass. The Korg DT-10 also suffers from a crappy bypass so I'm led to believe. 4 great true bypass tuners are:
Ibanez LU-20: Cheap, massive display, two outputs. I've owned this and I can't fault it, I only sold it because I fancied a tuner with a strobe mode. The best value option by miles.
Korg Pitchblack: Looks awesome in a stealth kinda way, lots of different modes including strobe. My current tuner.
Sonic Research Turbo Tuner: The most expensive of the three, but is the fastest most accurate tuner there is and has a great strobe mode. If I was buying a tuner I'd probably get this.
Digitech Hardwire Tuner: Don't know much about this one but it's worth checking out.