[jimboj]

This doesn't only happen with the two-prong adapters, I have noticed this on a few MacBooks, plugged in using the standard 3-prong UK plugs (sometimes with my phone too). An even weirder feeling is when someone else is touching the laptop, if you run your finger over their arm you'll notice the same bumpy feeling.

[zymhan]

Oh my god, this is the feeling my ex and I could never figure out. One of us would touch the other, and there was a weird vibrating sensation as one would move their hand along the other's skin. I can't believe I never thought that it might be the laptop.