We all have that one friend. You know, that guy/girl that thinks he/she knows better. They supposedly know more about everything and can't stop patting themselves on the back about how much of a godsend they are. A person so toxic that being in his/her presence destroys your confidence and makes you feels horrible about the person you are. You look at that person and think to yourself, "Dude, this guy/gal can have a whole conversation with him/herself and be content as a self-serving tool because he/she has no time for external input or feedback."