ass-kisser

A person who flatters or compliments somebody in order to gain their trust or approval; a goal-oriented individual who wants to ascend a hierarchical system (in a corporation or otherwise), and accomplishes this by getting on good terms with people. 'Ass' is a common and somewhat rude term for a person's rear end. Someone who 'kisses ass' is willing to degrade himself in order to please others and get ahead.