[Zoner]

Personality testing:
Recruit, The (2003)
Colin Farrell, Al Pacino

Farrell gets grilled by the CIA before entering their training program. They give him a battery of personality tests.


2 Different personalities not getting along:
Starsky & Hutch (2004)
Owen Wilson, Ben Stiller

Wilson is the slacker cop and Stiller is the "by the book" cop. Wilson goes to Huggy Bear for some information while Still is vehemently opposed to using such shady sources.


How someone learns to change thier personality in any way:
The Manchurian Candidate (2004)

An American soldier, son of a U.S. Senator and a ruthless political operative is captured in Korea, brainwashed, programmed to kill through a combination of classical conditioning and hypnosis, and rendered amnesic for the experience.