Similar to the Free Delivery Gift Scam, you get a call from someone telling you you've won the big prize in a lottery - to the tune of about $800,000. The caller will often try to get you excited and sell you on emotional statements like, "your kids are taken care of now" or "your retirement is well-deserved."
If you don't remember entering, they'll tell you someone else might have put your name in the draw. In order to get the money, you'll have to pay the state/provincial tax, something like 5% of the winnings.
Happy to get almost a million dollars, tons of victims send in the tiny 5% to a PO Box, after receiving a "confirmation" e-mail with the details on how the money should be transferred. This scam often targets older people and it's reported hundreds of thousands of dollars are lost every year to these scams.
How to avoid: you can’t win if you didn't play, so just hang up the phone if you don't remember entering.