an addition to the derogatory act of raising the middle finger, the opposite arm is raised simultaneously while flexing the bicep to give an emphasis of strength and intimidation.
note: at times an ordinary middle finger doesn't articulate the extreme disdain one might have for another, in these cases an atomic finger is more appropriate.
The other day I saw my ex-girlfriend holding hands with my best friend, so I dropped everything and gave them both an atomic finger.