CA-30

 All you will ever need
Unless you are doing scientific experiments, this is all the tuner any player of guitar, banjo, or fiddle will ever need. I would say other instruments, but these are all the instruments I can play.

A recent thread on the banjo-l list serve about tuners found that most of the hundreds of members of the group felt that the Ca 30 was all they ever needed. This included folks who report having used much more expensive tuners before the CA-30.

I have tried more extensive tuners, especially the Intellitouch which seemed very fashionable when I bought one a couple years ago. However, these tuners are easier to read, sturdier, and truly chromatic. They fit very handily inside even a small violin case or your breast pocket. They also have plug ins for using them with electric instruments or pickups on acoustics.

I would add that sometimes they are not as faithful if the battery is running down. I also find it can be a pain to use them because the dial is not backlit. However, that is something you just adjust to.

I have two guitars and two banjos and a fiddle. I keep two of these plus a Korg that is a version of this basic operation for guitars and basses.

This is all you will ever need and the only way to beat it for the money is to steal one!

 excellent
The display is very clear and easy to read and has a "dial" that swings left to right to tell you how close you are to whatever pitch you're trying to play. Comes with an electric input as well as a mic. It's very small and compact and the battery life is good. Great tuner at a great price.

 Excellent value -- I have 2 of these.
I prefer the older model a little more as it has better, more positive buttons - I usually find myself having to press on/off twice. Other than than it is superb. I have one velcro'd to my music stand for my electric guitar -- which I feed from my Marshall practice amplifier's line-out (or the effects line out of my other amp). The other, I use for my acoustic guitar (the tuner has a built in microphone), my son's & for checking the key/chords of tunes (that is a nice benefit of the "chromatic" part of this feature -- it will correctly detect & identify any and all notes). Batteries are cheap/common AAA & usuage is very low (the LCD is not backlit, so power usage is minimal). Stability is comparable to most other tuners including those costing $100 and more.

I recently invested in a Boss TU2 foot pedal tuner. I actually prefer the Boss -- it is brighter (for stage use) and, although technically less accurate than the Korg, provides more stable readings and hence allows very quick tuning. It can also be used as a mute switch and has a strobe feature which I never use. However, this costs about 5x as much as the Korg, uses more power (either wall wart or expensive 9V battery).

In conclusion, the Korg is excellent value at well under $20.

 Great toy
A lot of tuner for a buck. Probably the best out there. Compact, light, very precise, the built-in microphone is sensitive enough, maybe too sensitive, because it picks up the background noise. You can tune guitar, mandolin, ...., violin, cowbell, and use the input socket for contact mics.

 Great Value
I've never owned one of the more expensive chromatic tuners on the market, so I can't compare this Korg to one of those others. I can say, though, that I have no complaints about this piece of equipment. Having used this tuner for a year now (on the same set of batteries), I can't imagine why anyone would need or want one of the more expensive devices. If you want a cheap, effective electronic tuner, this is the one to get.

 Lifetime Guitar Necessity
The guitar needs this. The Korg ca-30 is one of the fastest working tuners for a lower price. It goes up and down the whole chromatic scale, so you're pretty much set. It also recognizes simple chords such as A, C, E and G. I have had mine for almost a month and it is holding up great. I have no regrets and i personally think it doesn't matter that it is plain black and not one of the shine-throughs.