Remove a stripped Case Screw?

That never happened to me with a PS3, but once on a PSP, once on a toy dog and once on an ancient laptop.

I tried to pry it carefully with pliers. To avoid scratching the plastic, I used the plastic pliers they give you with rubber office stamps.

However, in my ill fortune I was kinda lucky, as I found out that on the PSP the plastic thread was stripped, so pulling with the plastic pliers did the trick.

Have you tried also with magnetized screwdrivers? Do the other screws get out fine? On the ancient laptop, for example, I removed all the other screws, and pushed really lightly the top and bottom case, prying them with barely enough strengh to find out if the screw was still holding together. It didn't, but if it did, and if I had used too much strengh on it, I may have damaged the casing.

Also, the good old WD40 may be worth a shot, but I'd put it as a last resort card, and carefully applied. I used it once on a PSP, but then I managed to drop some in the innards, and got me quite a lot of time to clean all the mess.

As Philip said, a stripped screw may be pulled down in different ways according to the stripped part (screw threads on the screw, on the plastic casing or stripped head).

A careful use of plastic pliers may help you assessing the damage, allowing you to see if the screw budges or not.

Another attempt may be using a little bit of Krazy Glue to temporarily "fasten" screw and screwdriver, gaining more torque. However, there's still the risk of putting too much glue and leaving an unsightly blob.

I've also read about drilling the screw using a drill bit smaller than the screw itself, but as PS3 carries really small screws, and it's kind of a costly device, I'd avoid.

There are also specific screw extractors, and they sell them here.

Precision Screw Extractor Set