I don't have much experience in this area, but if you're thinking about robbing a bank, one of the keys to success is your ability pose a realistic threat to the tellers. You need some way scare and threaten the bank staff into immediate cooperation with your plan. If you show up and threaten to slap the teller, for example, you're like to get laughed out of the bank via an escort from the branch manager. That's why it's important to come prepared with some kind of weapon...a gun, a knife...even a well-sharpened stick might do the trick if you're intimidating enough.
But, like in so many other things in life, balance is important even when it comes to robbing banks. You want to pose a realistic threat, but it's possible to go over the top with your method of intimidation. A man named Marvin Simmons went overboard with his threats in a recent string of bank robberies. He never showed a weapon, but in each case he passed the teller a note threatening to detonate a nuclear bomb if the teller didn't hand over cash! Here's the story after a successful robbery in late February:
Surprisingly, Simmons succeeded in robbing at least four banks in Prince George's County, Maryland over the past few months with nothing more than his handwritten, nuclear note. I suppose the tellers can't risk calling his bluff, but I'm in awe that he was able to pull off four robberies with such a preposterous threat.
It's been a while since my last physics class, but from what I recall, a nuclear bomb creates a rather large explosion...one that would probably wipe all of Prince George's County off the map, bank robber and all. And while suicide bombings are certainly not uncommon, especially in some parts of the world, I have yet to hear a single case of a suicide bank robbery.
The good news is that Simmons was caught and arrested in Texas in late March. The bad news is that the ending to his story wasn't nearly as hilarious as it could have been. The perfect finish would have been an unsuccessful robbery that fell apart when a bold teller responded to his nuclear bomb threat by laughing and saying, "fine, go for it!" while calling the police.
Regardless, my advice to all the budding young bank robbers out there is this: when you make your move, don't get too swept up in the showmanship of the event. When choosing your weapon of choice for the robbery--whether that weapon is real or simply written threateningly on a note--strike that all-important balance somewhere in between Nerf slingshot and nuclear bomb. Stick to the basics, and go with a knife or a handgun. Fear is your friend, but it's gotta be believable...chances are, you won't have the dumb luck that Simmons enjoyed during his successful robbery streak if you go over-the-top nuclear.
Here are some links to the highs and lows of Simmons' robbery streak, from success to arrest: