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?
One who likes to tickle nipples. This can also be used to call someone a clown, jokster, goof, crazy, etc.. Some people you can just tell by their appearance that they are nippleticklers. Others it takes a little more research to discover this.