How can I de-ice a frozen car windshield or lock quickly?

Mix two parts isopropyl alcohol (70% or higher) with one part lukewarm water in a spray bottle and spray generously over icy glass. Ice melts almost immediately on contact because alcohol's freezing point is far below water's.

Start the engine, set climate control to the defrost position, turn heat to maximum with the fan on high, and switch air intake to fresh air (not recirculate). Warm air gradually melts the ice from inside the glass over several minutes.

Carefully warm the metal blade of your car key with a lighter or match for a few seconds, then gently insert it into the frozen lock. The heat transfers into the lock cylinder and melts the ice blocking the mechanism.