A useless phrase used in response to anything. Often said in the style the Doorman from the Wizard of Oz says "Well bust my buttons!" It is often used in response to something serious to throw the conversation completely off.
Guy 1: OMG I just found a pot of gold!
Guy 2: Well tickle my nipple!
Guy 1: Dude...my dog just died.
Guy 2: Omfg why dont you just tickle my nipple then?