Mute

I have discovered that the primary reason that phones have a mute function is so that when someone says, "It's really a work in process" for the fourth time during a conference call, I can gently press the mute button and scream into the phone, "IT'S A WORK IN PROGRESS, YOU STUPID @#%%$$!!"

Because holding in rage is bad. The mute button: Preventing Aneurysms Since 1974.