Yeah, mainly the pub, but also any situation where you want someone to do something that seems risky:

"Trust me, I'm a doctor!"

And dealing with unhelpful customer service:

"We're sorry Mr Smith but we can't do that..."

"Actually that's DOCTOR Smith"

It won't help you get what you want, but the amusement factor will make you feel better.

A friend of mine has Dr on all of his credit cards. He claims to have received free upgrades on rental cars from time to time as a result. Not sure if I believe that.