There are many ways to rip off tourists in Rome, Prague, Paris, and other beautiful European cities. Scammers have tried most of these cons on me. The best way to deal with them is to walk away without saying a word.
The Friendship Bracelet scam is where some guy starts wrapping string around your finger or wrist, effectively trapping you until they finish braiding an ugly bracelet and demand money for it:
In the Gold Ring scam someone will pretend to find a ring on the ground, give it to you out of kindness then suddenly insist that you fork over some money to reward their selfless generosity:
The Donation scam is where people, often pretending to be deaf come up to you and ask you to sign some kind of petition and then ask for money after you sign it. As a bonus, their confederate will pick your pocket:
In the Worthless Clothes scam some guy will try to give you crappy clothes under the ruse that they are very valuable then attempt to extort you: