I read a SF novel that I liked alot a while back, in which you could get a socket implanted behind your ear that would take a "personality chip". You could buy different personalities like J-Lo, or James Bond. The major problem is that, rather like when you are drunk, you FEEL as cool as James Bond, and affect some of his characteristics, but the people around you think, "Jeez, it's one of those miserable morons with no life who have to play at being James Bond to feel OK about themselves." Cool idea, tho.
How about a 'random' personality? You would have no idea what you were going to get. That would be fun. Of course, maybe you get Charles Manson one day and you end up with a life sentence.