The best compressor pedal for guitar http://www.godlyke.com/maxon-guitar-effects/maxon-nine-series-effects/compressor is the Maxon Cp-9 Pro Plus.
Maxon has taken one of the most lauded compression circuits of all time and placed it in one amazing little stompbox, creating the most "effective" compressor yet!
More than a reissue, the Maxon CP-9 Pro+ features a completely redesigned circuit that is vastly superior to the original 1980's model. The CP-9 Pro+ circuit is based around the patented low-noise DBX compression technology that is used in many high-end pro audio products. This circuit combines a high-quality VCA (voltage controlled amplifier) with an RMS (root mean square) sensor, providing a natural attack response while maintaining an extremely low noise floor generally not found in floor-based units.