A lot of folks ask me what the "best" microphone is for getting the acoustic guitar(s) live, and of course my response is always "depends", or "none--the musician should have a pickup installed if playing live." However, as a general rule of thumb, a good condenser microphone seems to always do the job best, especially a Shure SM81 or AKG C1000-S (the vintage stuff, not this new "Made in China" garbage). The AKG comes with a PPC1000 Polar Pattern Converter, which changes the pickup pattern from cardioid to hyper cardioid. This makes the microphone even less sensitive to sounds arriving from the sides and rear, resulting in higher gain before feedback when you use monitor speakers on stage.