I know this is a real grumpy old bag thing, but ‘No problem!’ when said e.g. by a waiter/waitress after you’ve said thank you for bringing whatever you’ve ordered.
Or ‘NOT A PROBLEM!’ at full volume, which came close to making me want to scream on a holiday in Oz, when they practically yelled it every single time.
I so badly wanted to say, ‘Well, I’m glad it’s not a problem, since it is actually your job to bring what I’ve ordered.’
(As I said, Grumpy Old Bag!)
We broke the return journey in Singapore, where dh has relatives, and oh, the relative peace of quiet, efficient, unobtrusive service.