Any one know how to open this screw?
Tried pliers but no avail and standard box of security screwdrivers couldnt open it.
Here are some more photos
How to remove this screw
screwdriverscrewsSecurity
Related Solutions
If the wall is standard drywall, I would use a punch, wooden dowel or something similar and push them in. By design they are resistant to pulling out with out some wall damage. They just need to be slightly below the surface. Repairing the holes will depend on the wall finish. If it is painted then spackle as @Craig suggested, and repaint. If it has wallpaper with and intricate pattern you can try to use small pieces (providing you have some extra) cut with a paper hole puncher and glued in place.
Definitely a "hex/Allen/socket" head set screw, you can plainly see the hex in your picture if you look close. I think you may have been using too small a key:
Best Answer
Those are external line head screws, and are used as anti-tamper screws in some Japanese electronics. You can probably find a driver for them from a game console hack supplier (they're used on Gamecube, Wii, and some other game consoles). The driver looks like this (sorry for the horrible pic):
They also come in 5 and 7 point varieties (hard to tell how many points from the picture you posted). I've also seen them called torx inverted.
If you don't want to get a specific driver for them, you can probably get them out by clamping on the head really hard with a pair of vise-grips or use a screw extractor. You might be able to find a socket that will mesh with them well enough, but that's a long shot.