I've never found one that I particularly love, but then again the only time I play acoustic shows are at small quiet coffee houses, So I haven't had much to do with clip-on tuners.
For my personal tuning endeavors I prefer my Korg. It has input, can still pick up acoustic in louder environments (Like when my music is on) and can be set to go three steps down or so. Also works well with my bass. Oh and it can shoot people I don't like and take forensic blood samples, which is fun for those crime scene gigs.
EDIT: That was my 200th post
Make Awkward Sexual Advances, Not War.