BehinD the MAsk.....

Outside of battle, Trowa Barton has a job at a circus, where he performs as a clown. As a clown, Trowa wears the traditional baggy pants and weird frilly thing on the neck (whatever you call that), but instead of grease makeup, he wears a mask painted like a clown's that covers only the right side of his face.  Many people think it just looks cool, but I think there's a deeper meaning to Trowa's mask.

Trowa is the type of person who rarely ever lets his emotions show. Psychologically speaking, he wears a mask of apathy, hiding his feelings
behind a calm exterior. There is even significance in the fact that the mask covers only half of his face; Trowa's apathetic demeanor is incomplete, as he allows his feelings to show from time to time despite remaining almost unwaveringly calm. Most noteably, the usually thoughtful Trowa acted on impulse when the target Catherine was on was seized by OZ (this was when he hijacked the Wing Zero because the adjustments to Heavyarms were incomplete). At times, Trowa has spoken of how pointless war is, usually to
Quatre. In short, Trowa only hides about half of what he feels, which strengthens the symbolism of his mask.