Sometimes, the smallest bit of luck/random kindness can just completely make your day.
Event: I left money in a vending machine so that someone could enjoy a free beverage. Obviously, the cost of a soda is negligible- it's the surprise that was meant to bring cheer.
Reactions: Once again, I wasn't around to see the reaction on this one.
Would I do it again? Yes.
Cost: A dollar.
Time: About two seconds.