Defining: Optimizer, Powergamer, Munchkin

[AstralFire]

Optimizer: Someone who decides upon a set role or concept and uses the rules to maximize her potential towards that direction. An optimizer may be optimizing a non-optimal class or concept for the sheer enjoyment of making that concept work.

Powergamer: Someone who decides upon a high level of potency and makes character selection and customization primarily based upon being effective. A powergamer begins character creation with a mechanical effect or level of dominance they seek to achieve.

Munchkin: Someone who decides upon a high level of potency and makes character selection and customization solely upon being effective. May or may not actually use flawed rules interpretations or cheat; the important thing differentiating the Munchkin from the Powergamer is a near-total apathy for assisting or refraining from injuring the play experience for others, in pursuit of her goal of power.

There is a rough correspondence on the other side of RPG, the 'RP' - those would be Method Actor, Limelighter and Prima Donna.