While it's nice to be able to run into Wal-Mart for a couple pairs of socks without having to drag a kicking, screaming child down the aisles with you, it's illegal to leave children unattended in your vehicle.

If you're found in violation of this law, you can be fined and sent to a mandatory community education program, or even worse if the child in question is injured as a result of your negligence. For example, if their ejector seat is activated while the sunroof is down.