i rarely use the ATM... but when I do, it's always with my left hand. My right hand is holding a glock the entire time, of course. I run that whole cash pickup operation like a military operation. Paranoid as hell, as one should be.
and the correct response (if you dont have your hand on it) isn't to deliver some Dirty Harry line to the bad guy. it's more optimal to burst into tears if he does get the drop on you. Then he will smirk and let his guard down a bit. Then you smoke his bitch ass, of course.