"Keep the change, mate"?
Preferably to someone older than you, before walking off with a smug feeling inside, safe in the knowledge that you are the living embodiment of cool.
I ask because this because I just can't help myself at the minute. Pubs, clubs, food vendors and now ice cream men, they all get my ill-gotten cash. I just bought 3 ice cream cones and nonchantly told the ice cream man (who looked exactly like one of the Chuckle Brothers) to keep the £1.60 odd change. As i walked off with my creams I felt this all consuming feeling that I i had become some sort of philanthropic demi-god.
My inner cool levels would be even higher if, on my walk to get the ice creams, the van hadn't driven off slightly, I hadn't dropped to my knees Platoon style, screaming "Noooooooo!!!!" infront of some scared children, before the driver heard my desperate cries and slammed on the breaks before serving me with a knowing smirk on his face about the power he holds over all.