A Sociopath

A sociopath is typically defined as someone who lies incessantly to get their way and does so with little concern for others.  A sociopath is often goal-oriented (i.e., lying is focused - it is done to get one’s way).  Sociopaths have little regard or respect for the rights and feelings of others.  Sociopaths are often charming and charismatic, but they use their talented social skills in manipulative and self-centered ways (see, lovefraud, for more on sociopaths).

http://www.truthaboutdeception.com/lying-and-deception/confronting-a-partner/compulsive-lying/types-of-liars.html

The Sociopathic Liar – Beware of this Dangerous Sociopath

http://www.compulsivelyingdisorder.com/sociopathic-liar/