I love Macs but the startup sound when you open the computer and specially the fact that you can't turn it off just looks so 1990… and it drives me crazy. The sound comes from the internal speaker so there's nothing you can do to minimize the volume or shut it down.
My office is in the corner of our bedroom so if I decide to work after my wife is already asleep, sure thing the startup sound will wake her up.
Gladly I found this little utility that let's you control that. I now install it as one of the first add-on to my Macs.
And it's free!