Voltage doesn't kill, current does. One can easily take 10s of thousands of volt across the the heart if the amperage is low, but a car battery putting out 12 volts and several amps can. Personally, I've taken leads from a 240V, 3KW solar panel array from hand to hand and not felt a thing. Have so same 2 leads touch the same hand, you're going to feel it. For me, felt like a snake bite, minus the venom. Left a few small red mark on my hand that cleared up in a few days.

Mind this is all in reference to DC current. AC is another beast.