From Aeon Group:
Digital Guitar Tuner is a free Windows software, which let's you accurately tune your guitar using direct input, microphone, or MIDI tones. Digital Guitar Tuner features 27 tuning types. This version is the first release on CNET Download.com.
What's new in this version:
This version is the first release on CNET Download.com.
Very simple and intuitive, yet provides lots of different tunings for those who need them. Appears to be very accurate.
The percentage indicator seems to be useless, as it doesn't deviate by more than a couple of points from 100%, regardless of how far off a note is from the mark (but the needle on the left is accurate and is quite sufficient to complete the tuning). Another would-be-nice-to-have feature: to display the note being played, as an absolute frequency (and by the nearest letter).
This is a useful little program, very much worth the download!