I recently got me a digital guitar tuner.

Pros:
- digital
- chromatic: you can tune your guitar to any note in the musical spectrum
- variable pitch from 435hz - 445hz in 1hz steps
- 2 modes:
— automatic: tuner detects nearest note
— manual: choose the note you want to tune with
- 2 receivers:
— 1/4″ input for electric guitars
— built-in mic for acoustic and classical guitars

Cons:
- strict tuning

Actually the strict tuning becomes a good thing… at least you get a perfectly tuned guitar. It is just quite a hassle at first.