The M9 is one of the rarer sidearms in DayZ, but is useful for raiding towns and cities thanks to its low noise level and good iron sights. Due to its low damage and rare ammunition, the M9 is one of the least desirable sidearms in DayZ. Its silenced variant, the M9 SD, is much more desirable thanks to its silent killing ability.
This page contains information about the mod version of DayZ. Standalone information is available here.