[mikeash]

Short the terminals of a 9V battery with your finger. Now unscrew an outlet cover and short the terminals within with your finger. Notice the difference. (Note: don't actually do the second one.)

People love love love to repeat this tired "it's not the volts that kills, it's the amps" line, while completely ignoring the fact that low voltage makes it really, really, really hard to obtain the necessary amps to be dangerous.

[njs12345]

I agree entirely. Nonetheless, here's an interesting story about someone being killed by 9 volts: http://www.darwinawards.com/darwin/darwin1999-50.html

[mikeash]

It's interesting both because 9V killed the guy and because he had to try pretty hard (stabbing his thumbs) to achieve it. So, while dangerous, not nearly as dangerous as e.g. 110VAC.