If you want to crash your Mac, or perhaps any kind of computer, put a little piece of aluminum foil paper inside the USB connection of an external device and then plug the device in, while your computer is running.
In my case, it worked: the Mac spontaneously rebooted. After 2 reboots I realized that my Mac experienced a real physical problem and found the culprit inside the connector of my USB stick. It was the result of keeping the USB stick in my pocket, along with some random other stuff, aparently including some aluminum foil paper.
So: be warned :-)