The one that freaks me out is the urban legend about people who drug you and remove your kidneys and other vital organs for sale on the black market.

The basic plot is that you meet an attractive stranger at a bar who then buys your a drink or slips something into your drink. You then pass out and then wake up in a bathtub full of ice with an aching pain on one side of your body. When you examine your stomach area, you notice a scar which then tells you that they have just harvested your organs.

If you're lucky, they only removed one kidney and if you're unlucky, they've removed both kidneys and you'll need dialysis for the rest of your life. Either way, you're screwed.