I play music as loud as I can handle it and paint. I find that usually by the time I'm done painting I've calmed down. The music is an essential part, or else I can't think of what to paint. M.I.A., vitalic, animal collective, crystal castles, meat loaf, etc, all seem to be the most helpful.
Writing also helps; I like to write horror. For whatever reason, writing some incredibly gory short story is a wonderful method of venting for me hahaha.
Either that or crying, but crying often leads to a panic attack so I'm trying to find ways to stop myself from crying before it escalates.