glue your screwdriver to the screw and gently screw it out
Can't desecrate a tool :-D
If the screw is in plastic... you might be able to heat up the head of the screw with a solder iron... then use a screwdriver... but only if it is not TOTALLY stripped. One way to avoid stripping screws is to STOP turning it when you realize the screwdriver is not getting a good "bite" on the head. That indicates your screwdriver is the wrong size or shape to fit the slots. With the wrong screwdriver, you will get a weak "bite" and it will strip the head. Another method that often works is using a very pointy small wire cutters to GRAB the screws head and turn the screw out . That only works if the screws head is NOT FLUSH against the surface. The dremmel methods mentioned by seandogue are the most excellent.
Thixotropic Super glue or epoxy a small long screw and unscrew them togetherunless you are the klutz who stripped the head. Then go to a friend for help.A
You have a few options, depending on how accessible it is. You can try something like an easy out, you could use a dremel to cut a straight line in the head for a screwdriver, or instead of an easy out you could try using a left-handed drill bit, which is basically the non-specialized version of an easy out.
well...careful use of a Dremel and engraving bit *might create a channel deep enough to use a flat-blade screwdriver, or you could drill into it in aside by side fashion with a small (.020) drill bit to form a new channel, or you could drill a hole into the center and sacrifice a small flat-blade screwdriver by driving it into the hole. with a bit of super glue for additional strengthener. I've used all three methods in the past for stubborn screws. The first tends to wipe out the engraving bit if you're not careful, the second can be effective is augmented with an engravers bit to finish it off, and the third, well, that can be hit or miss but has proven effective most times I've had to employ it. Means re-shaping the driver tip once it's been extracted from the screw though.The final one is slightly more destructive and requires a bit of damage to the case. Use a ceramic cutoff blade to square the screw and then use pliers to turn the screw. Unfortunately, the case gets cut marks in it.