Ive had someone completely ignore me when I said "Hello!" quite loudly, as they looked me in the eye. 5 minutes later they were looking for something and said "Hey" to me. I completely ignored them back.
Then he comes back with a louder "I NEED HELP" so I turned and asked him what he was looking for. I told him the exact opposite direction, disappeared out back and watched him desperately look for it on a wild goose chase on the cameras. Curses and all.
It was....glorious.