*** PLEASE NOTE: If you have external speakers or headphones then StartupMute cannot silence the startup sound. This is a restriction of Mac OS X which will only allow apps access to the default output. Unplugging the speakers or headphones will allow the app to mute the startup sound. Apologies for this, we're working on a way of working with these limitations. ***

StartupMute does one job, but it does it well. When starting up, your Mac will play the startup sound at the same volume that was set when you shutdown. StartupMute silences your Mac when you shutdown or sleep meaning you aren't disturbed the next time your Mac starts up.

Also has the option of restoring the volume after startup if auto-launch is enabled.