Korg CA40 Chromatic Tuner
Also consider the New and Improved Korg "CA50" Chromatic Tuner!
Full of features and super compact. Automatic and chromatic tuner and reference pitch generator. Large LCD screen with simulated LCD tuning meter, three bright LED tuning guides. Chromatic tuning range from A0-C8, calibrates from A410-480 Hz (1Hz increments). Generates C4-C5 (1 octave) reference pitches through an internal speaker. Includes built-in microphone, auto power off, and 1/4" input and 1/4" output jacks. Requires two AAA batteries (Included). Size 3.94" x 2.64" x 0.67".