Multiple Personalities
Something in the character's past has caused his personality to fragement into a number of distinct selves, each with its own traits, outlooks and agendas. The number and nature of these personalities should be agreed by the player and Storyteller, as should matters such as the trigger to switch personalities (often emotional stress) and the knowledge each possesses. In Cainites, these personalities may exhibit different Virtues, traits and Disciplines, and they could even believe themselves to be of different clans. However, only the Storyteller can decide if the skills exhibited by a personality are real or delusions.
Munchkins beware: Allowing different personalities access to different skills is not an invitiation to power-game. The total number of skills available to the character is a function of the character's creation and experience. Each personality has access to a limited subset of the whole.
Players who insist on dividing their characters into hyper-specialized sub-twinks should remember that this is a derangement - a drawback. Rambo is likely to manifest and attempt to "destroy the enemy" when the character is faced with adversity in Elysium, while Bambi just might try to flirt her way out of a Sabbat attack. -Just my two cents. Jamie.