Q:

What is this screw's name / type? 

Seems that recently Ikea and many other menufacturers are using the screw you see in picture (classic 1.5 multi power plug, nothing fancy).  
I have never seen anything similar and searching online didn't help much. 
Can you please suggest its name so that I can buy a specific tool to unscrew it? 

A:

That is one version of a security screw, there are several types. 
Used to try to make items not easily opened by the masses so you have to buy another instead of fixing something simple...
Depending on how deep they are I have used needle nose pliers or made a "socket" for them - I see those as a challenge and have boxes of "ordinary" screws to replace them.