- Square, Robertson drive
- Security Hex (top), Hex (bottom)
- Security Torx (top), Torx (bottom)
- Spanner-Head, Slotted Spanner, Snake-eye, Pig-nose
- Slotted, Standard, Flat-Head
- Hook/Eyelet driver
The square drive, or Robertson (named after Peter Lymburner Robertson) is a great type of screw head--one I use for woodworking, in addition to the torx, whenever possible. The recessed square in the head of the screw holds the tool very well which helps keep the tool from slipping out of the head and force is easier to apply.
The Spline drive is one I've never used, but would no-doubt be useful in scenarios which high torque is needed. The drive is similar to a torx except that it has 12 splines.
The Pozidriv is just like a philips drive except that it has 2 crosses, one thick and one very thin. The idea is to better resist slipping out of the head, and to more easily apply torque before slipping out. Looking down, there are 8 total points, 4 broad and 4 narrow, each set 45 degrees apart.
The Internal Hex drive, and safety or security hex drive is seen often on set screws, and Allen wrenches are usually what I use for these type heads. The security drive can be used for non-security type hex heads, but not vise-versa. The security hex head will have a raised post in the middle making it impossible to insert an Allen wrench or non-security type hex bit into the head. Hex heads are useful for their ability to transmit more turning power than some of the other types of heads. External Hex is generally what you think of when you think of a 'normal' bolt.
The Torx drive is similar to the spline, except that it has 6 distinct splines. I have seen star shaped security heads that consist of 5 splines (I believe called Torx Plus Security) but I think the proper term for 6 splined drives, in my mind anyhow, is Torx. Torx Screws are used pretty commonly in the automotive industry (including the security-type), and with increasing popularity in woodworking and electrical applications. There are also external Torx bolts.
The Spanner drive looks just like a slotted screwdriver except on the tool, nothing in the middle. In a pinch it's easy to grind or cut the middle out of a cheap slotted screwdriver to use as a spanner drive. Looking at the screw will make it easy to see why this drive is also called snake-eyes or pig-nose. I've only ever seen this type screw head used in electronics, but the purpose is to reduce the amount of torque that can be applied.
The Tri-wing screw has 3 fins and a triangle shaped hole in the middle. It's used in the aircraft industry, but I've also seen it occasionally in some appliances around the house.
A slotted or standard screw is the oldest and most popular kind of head. It's also the biggest pain in the butt, I think. The tool slips out constantly and more time is spent putting the tool back in the screw than actually working. It's easy to damage the screw and the work area and sometimes yourself. I hate standard screws.
The Torq-set drive is very similar to the Philips head except that each fin is offset so none of the fins continue across the center. The end of the drive is less angled than a Philips head, so more turning power can be delivered before slipping out. This is another of the drives I have never had to use.
Last in the picture is a drive to help more easily use eyelets and hooks. It's handy for smaller hooks and eyelets that are more challenging to grip and push at the same time.
Not pictured but worth mentioning are one-way, Philips (duh), triangle, and TP3 drives. The Triangle drives are commonly seen on toys, and the TP3 is very similar to the triangle except that it has curved sides. Unless repairing Gameboy's is one of your hobbies, the likelihood of ever needing a TP3 is slim, I've never seen the TP3 anywhere else. The Philips was a stupid thing for me to leave out. It's about as standard as the slotted screw anymore and is used in just about every application. The ability to transfer torque is better than the slotted drive but not by a lot. The biggest advantage over a slotted drive is the decreased slipping, and the tool will stay centered much more easily until turning power increases.