One of my laptops is running with a counterfeit charger (Amazon) and a counterfeit battery (eBay). As soon as I realized that I have never left it plugged in where I don't see it - who knows what kind of fire hazard it could be.

Also, lasers. There are plenty of illegal laser pointers on eBay and output rarely matches the claims. And you really don't want to play with these illegal lasers unless you have real wraparound lenses.