Pan head
A low disc with chamfered outer edge
Button or dome head
Cylindrical with a rounded top
Round head
Dome-shaped, commonly used for machine screws
Truss head
Lower-profile dome designed to prevent tampering
Flat head or countersunk
Conical, with flat outer face and tapering inner face allowing it to sink into the material
Oval or raised head
Countersunk with a rounded top
Bugle head
Similar to countersunk, but there is a smooth progression from the shank to the angle of the head, similar to the bell of a bugle
Cheese head
Disc with cylindrical outer edge, height approximately half the head diameter
Fillister head
Cylindrical, but with a slightly convex top surface. Height to diameter ratio is larger than cheese head.
Socket head
Cylindrical, relatively high, with different types of sockets (hex, square, torx, etc.)
Mirror screw head
Countersunk head with a tapped hole to receive a separate screw-in chrome-plated cover, used for attaching mirrors
Headless (set or grub screw)
Has either a socket or slot in one end for driving
Square head
A 4 sided head used for high torque driving with a wrench.
Some varieties of screw are manufactured with a break-away head, which snaps off when adequate torque is applied. This prevents tampering and disassembly and also provides an easily-inspectable joint to guarantee proper assembly. An example of this is the shear bolts used on car steering columns, to secure the ignition switch.
