Once I strongly hissed at my boss from that time in a "stop now or I start yelling" voice.
We had an emergency and I was already working late to fix it. 8pm, only the both of us were still in the office. I was in the zone, still searching for the source of the problem and he kept coming in every 2-5 minutes offering his help, ripping every shred of concentration right off my skull, but he had absolutely no relevant technical skills, experience or information. There was nothing he could do.
In the end I hissed at him "Get your fucking ass out of here and let me do my job. This piece of shit kills my day and there is nothing you can do besides to say 'go home'."
Then he finally let me do my job.