to punch my colleague in the face?

[TooOldForGlitter]

or perhaps staple his obnoxious paisley patterned tie to the desk and knock his carefully lined up pencils into shocking disarray?

His crime? I make him a coffee, I put it on his desk, he doesn't say thank you. It happens at least twice a day! AND if he offers to make a drink he sticks the kettle on, walks away, leaves it and I end up getting up to do it.

This is not a real problem. Just don't make him a drink. Sweet cheeses. Next.

Superglue his pencils together when he isn't looking. Just to help them stay neat.

do what ZacharyQuack suggests and come back and tell us how it went .

Stop making him coffee. Immediately.

Next time make him a coffee, put it on his desk, if he does not say "thank you"

Put a ginger nut biscuit, flat on the surface of the coffee, leave it floating.

when he asks why or comments, "I made you coffee, you didn't say thank you, which takes the biscuit'

It works every time, he will never forget again.

Put it down in front of him. If he doesn't say thank you, take it away again. If he triea to snatch it back, hold on and say "what's the magic word?"

Get a mug printed with "It's good to say thanks"on it.