My Grandfather- ‘well I’ll go to th’foot of our stairs’ when hearing something that shocked or surprised him. Said in his strong Lancashire accent that’s hard to reproduce in writing.
My favourite is by Dorothy Parker and I use it quite often to turn down an alcoholic drink which I don't want, without offending the person who's offering the drink:
"I'm really not much of a drinker Just one or two at the most. Three, I'm under the table Four, I'm under the host"