Name: Silent Start
Mac Platform: Intel
OS version: 10.9 or higher
[Fixed] Startup chime not muted on some systems.
[Fixed] Misc minor bugs.
[New] Showing alert if headphones are plugged in when restarting
Courtesy of C.O.R.E
Ever had to restart your Mac and you (or someone else) has been annoyed by the startup chime? If so, give Silent Start a try today. It's able to silent the chime and then restore the volume back to normal after it starts up.
The only exception is if headphones are plugged in, and in that case OS X doesn't allow Silent Start access to the internal speakers. However, Silent Start will show a helpful dialog right before restart/shutdown to give you a chance to unplug them so it can mute the startup chime.
More info: http://www.tunabellysoftware.com/silent_start/
Mac App Store: https://itunes.apple.com/us/app/silent-start/id905747757?mt=12&ign-mpt=uo%3D6