I tend to only see them in Waitrose getting there free coffee so when I pass by I make a conscious move over to say hello with my hand outstretched. This tends to unnerve them so with a big smile & friendly positive demeanour I look them straight in the eye I say hello how are you? Then when they reply & ask how I am I tell them all the positive things that have happened in a quick & condensed fashion, close with a yes, I feel truly blest & then say oops I'm late for an important meeting & leave very happy & content. I can't help chuckle when I see the look on there faces.
The best revenge is just being happy, it throws them every time