Strobe tuners are the holy grail of instrument tuning, offering accuracy within one tenth of a cent. Since a reliable standalone strobe tuner will set you back $75-$100, most guitarists make do with more affordable chromatic-style tuners.
Pros: Precise, professional tuning that can be applied to guitar, bass, brass, and woodwind instruments. Internal signal boost allows for direct input of guitar with a cable adapter. Noise filter helps to reduce affect of ambient noise on tuning accuracy. Concert A reference mode allows for piano tuning.
Cons: Requires a $13 instrument cable adapter for direct guitar input. Incompatible with first-generation iPod Touch, and second-gen Touch owners will need to purchase a microphone accessory or cable adapter.