The tips of some screwdriver bits have been brushed with a thin layer of diamond particles.
Manufacturers of diamond-tipped screwdriver bits claim that they grip the screw head and hold it more securely when screwdriving.
Tungsten carbide-tipped bits
The tips of some screwdriver bits have been brushed with a thin layer of tungsten-carbide.
Manufacturers of tungsten-carbide tipped bits claim they offer:
A better grip on screws compared to other types, meaning they are less likely to slip out of the screw and damage the work surface
Increased resistance against the bit becoming worn over time.
Ribbed-tipped bits
Some screwdriver bits have indentations (or ribs) in the surface of the screw tip
Manufacturers of ribbed-tipped screwdriver bits claim they offer increased grip between the bit and the screw, compared to other types, so there is less chance of the bit slipping out of the screw.