Here’s several just off the top of my head:

  1. When people throw pills into their mouths and don’t wash them down with water.
  2. When people don’t say “goodbye” before hanging up the phone.
  3. When people don’t lock the doors of their cars before leaving them.
  4. When people push food around their plates for several minutes without putting any in their mouths.
  5. When people are very obviously drunk or stoned and then miraculously sober or straighten up in the blink of an eye.

Feel free to add to this list.