Maybe you thought we knew all there was to know about the ordinary house gecko? Not so:
[O]nly now have scientists discovered how the tail plays into the gecko's ability to climb the seemingly impossible. The scientists tested the geckos on slippery vertical surfaces and found that when the lizard loses its grip it presses its tail to the wall to keep itself from slipping. The gecko could fall back as much as 60 degrees and still manage to right itself using its tail. ...
High-speed video was required to see the tail in action, since the movement occurs in milliseconds. Incredibly fast lizards, geckos can travel up vertical surfaces three feet per second, taking 30 full steps each second.
The gecko's tail was found to have another unique use. The same researchers tested the gecko's response to falling from high surfaces and found that the tail was just as vital here as it was in climbing. In freefall the gecko rotates its tail to maneuver itself so that it will fall always feet first—such a maneuver taking only a tenth of a second. Once righted it then spreads its legs and toes to create what scientists call a parachuting effect.
They're hoping to use the research to design new robots with gecko-like "active tails" (which, no doubt, will be used one day to enslave the human race). Very nifty.