Allen keys, if they fit in a hex-shaped socket. They are used on all sorts of stuff, since slipping doesn't strip the head like a philips (cross) or slotted screw would, and it doesn't scuff the surface. I learned about a cool "ball head allen key", which lets you use it at up to a 45 degree angle from the work surface.
The square-hole kind are Torx; they allow power tools to apply more torque, and thus to make automated assembly faster. Most common use is on Macintoshes. (T-10)
I have all sorts of these drivers, since satcom equipment uses them, often multiple types on a single assembly.
I've gotten lazy in my old age, and if I need to screw something, I'll use a bit in a ratcheting screwdriver, vs. a regular one. Or MAYBE a power screwdriver, but I don't have a good/small one, and it's also easy to mess up with those.
Just curious, are you British? Brits call them either Allen keys or hex wrenches, while Americans call them either Allen wrenches or hex keys.
And yeah, the ball-heads rock.
I usually call the individual ones provided as part of ikea "keys" (allen or hex, interchangeably, but she was looking for something other than hex)
If it is as part of a larger hardware set, or a comprehensive size array, I'd call them allen wrenches. Never "allen key set".
I lived in London and offshore-UK for a while. I guess that's when I started doing hardware stuff, out of necessity; before that, I was pretty much a crypto/math geek exclusively, and didn't deal with anything except on-computer.
Of course, after the caribbean, offshore, and Iraq, I am pretty comfortable doing most mechanical/electrical/hydraulic things. I wish I could be an A&P mechanic in skill level (I've worked with some, and they're pretty much the only "mechanical" people, other than mechanical engineers doing design-for-production, that I'd trust with anything critical)
I've got a small set of Torx of the sizes required for opening xboxes. :) Total coincidence there. And.. they're star-shaped! I've seen those oddly shaped 'new' torx or something that look vaguely squareish but I think it may be a different brand name.
The Ace Hardware at Festival City is finally almost very nearly a real hardware store. It's no Home Depot or Lowe's, but it's huge and I was finally able to buy some PC-7 epoxy in Dubai. :)
I meant star shaped, not "scuare" shaped. The handles are usually squared, but yes, the heads are designed with a pattern so 1) you can apply more torque 2) mis-inserting the tool doesn't mess with the socket.
Square drive is probably just the power tool 1/4" square drive, used for fasteners. I've seen this done too.
I must go to this Ace. I was pretty happy with the Ace at BurJumann, for the size. The "GMC" ultra-cheap australian/chinese powertools are actually decent.
I'm always going to the new ace. It's huge like, huge. Still not as awesome as hardware stores back home, but they've got an entire aisle devoted to adhesives.