The KORG GA1 can be used it to tune a electric guitar or bass guitar, and it's so easy to use, and does exactly what is says on the tin. It can be used by plugging into it (electric guitars), or acoustic guitars.via its built in microphone. The GA1 doesn't come with its own stand, but it has a slot in the back so you can push a spare guitar pick into it, and stand it up. Comes complete with batteries, and good instructions. In my opinion, for the money you can't go wrong with the KORG GA1
Korg GA-1 LCD Guitar /Bass / Acoustic Digital Tuner
The Korg GA-1 features a digital display and green/red led's to clearly show the tuning of your instrument. It will even tune 7 string guitars and 6 string basses and has a built in ultra sensitive microphone to pick up the tuning of an acoustic guitar.
Ultra-compact design. High-precision LCD needle-type meter for stable tuning. Quinta Flat Tuning mode lets you tune 1--5 semitones flat Supports 7-string guitar tunings. Sound Out can produce a reference tone from the internal speaker. Auto Power Off function conserves battery life. Approximately 100 hours of continuous use.