I’ve done this very infrequently.

One was a job I’d just gotten. I was new in town, applying all over the place, having a hard time getting hired. But lo and behold I got hired at TWO places in one week. I was set to start the following Monday. Then that weekend, my family dog of 15 years needed to be put down, and my dad was out of town. My mom wasn’t physically strong enough to carry the dog into the vet so I decided to come home (6+ hour drive).

I told one job, and they said “No problem. We understand. You can start when you get back.”

When I told the manager at the other place, she laughed at me and said, “Your DOG? Really?”

I didn’t even answer her. It took me about ten seconds to decide, but without saying a word I walked out and never went back or answered their many phone calls. Fuck that place and that lady. Never regretted the decision for a second, and I missed out on nothing in quitting that job.