Tuner - quite unoriginal name of the program, at first glance you even can't say what instrument is this tuner for, but the program arhive is called guitar.zip and the program name is "Tuner", so you can guess it's a thing which you are looking for... However, I would say it's not worth downloading because sound quality is very bad and there is no feature to use microphone, so you must have an ear for music, but if you can tune by ear, why should you need tuner? One more thing, all the program is the main form and about window, so why the hell it weights 1,4 mb. This simple program even needs installation, but there is no shorcut to uninstall it. All in all, this is not a real guitar tuner, maybe a student's try to check his programming skills.
Rating: 4/10
Download link: http://www.dreadscott.com/download/guitar.zip

Guitar Tuner - the design of the program is not so poor as the previous and sound quality is a lot better, you can choose between acoustic guitar sounds and electric guitar, but there is only one, standard E A D G B E tuning and again, no microphone feature. The same problem is in program size: 3,2 mb - I thought this software will have more features. In conclusion, Guitar Tuner is better than the previous application, but not a one I would use.
Rating: 6/10
Download link: http://www.gch-guitaracademy.co.uk/freeware/GuitarTuner.zip

Audio Phonics Guitar Tuner - Audio Phonics made a good job and created simple, full of features and the most important - free guitar tuner to meet all your needs. AP Guitar Tuner (only 1mb size) has got microphone feature, so you can plug-in your guitar directly to computer microphone or line-in port, or if you have acoustic, place the plugged in microphone near your guitar, and start the application. When you hit a string, program shows percents away from the root note, for example +15% means that your string is tuned too high. Moreover, there is over 40 tunings not counting a standard one and you even can create your own. The only minus I have found was not working "Help" button, but AP Guitar Tuner is too simple that you would need help, though it's included in installation dir, called APGTHelp.htm. To sum up, this is a best choice out of three and I will use it myself.
Rating: 10/10
Download link: http://rhythm.harmony-central.com/~ftp/software/windows/guitar-bass/apguitargsetup.exe