You can touch both terminals of a car battery with one hand and nothing will happen. If you short both with jumper cables it will spark. Maybe if you connect both ends to one side of a door handle it will heat up, I guess it depends on the material in the door handle and how conductive it is?

People say it's not about the voltage, it's the amperage and stuff all the time. The current running through your body IS what damages it, but in truth both are related to each other - higher voltage means higher amperage. For it to be dangerous to a human being, you need high voltage. High amperage comes from high voltage and/or low resistance, and human flesh/organs etc have a high electrical resistance. Typically anything below 50VAC or 120VDC is considered safe for adults to touch under dry conditions (I think that's in an IEC standard somewhere)