Lockpicking skills come in handy in those situations. This reminds me of the time a friend got locked out of his car, but his trunk was open. The car only had 4 doors, however, so it wasn't much use.
In the trunk was a broomstick, some rope and a, erm, we call them "parrot wrenches". Fortunately, one of the rear speakers could be lifted up a bit, so I fastened the wrench to the broomstick with the rope and slid it through the small hole (it was just enough to fit). Through that small hole, I manoeuvred to the rear door lock and pushed it up.
All my friends remember that MacGuyver moment to this day.