I like...

... observing people and their inner contradictions.
... making questions whose answers contradict their behaviours.
... observing how they don't realize what you've just done... and the arrogance that emerges from the superiority they feel they can brag about.

Then I silently switch off the light, close the door, and walk away.

(This deserves a deep writing, but I don't have time now for explaining. A pity; I'd like to).