As interesting as the design of handguns may be, the human factors design of the holster is just as intriguing. Easy access, safety, security, comfort, and durability are all vital to the perfect holster design.
The belt holster is the most basic variety and also the first one that comes to mind.
The paddle holster is designed for easy and frequent removal (usually by detectives) and sandwiches the pant waistband between the holster and a ping pong paddle-shaped board.
A common military accessory, the thigh or tactical holster is strapped both around the thigh and to the waist. This secondary location doesn't interfere with a rifle slung across the chest and can be easily accessed from the crouching position. However, a thigh holster is awkward to access on the run.
The chest holster is designed for easy access inside a vehicle and is compatible with the new military uniform standard nylon webbing MOLLE.
For true undercover agents, the concealed holster shirt hides a handgun underneath your CIA-standard khaki button-down.
Perhaps only actually used in The Matrix, the dual holster seems a little overkill (no pun intended).
The ankle holster is perfect for last-ditch efforts or surprise attacks while tying your shoes. But I doubt a handgun on the ankle is comfortable to wear for long.
Holster design has come a long way since the Wild West. Many modern holsters include a gestural lock or combination of movements that need to be performed in order to remove the gun from the holster. This prevents, say, a criminal from taking a police officer's handgun during a fight.
However, ask any police officer and they will tell you that their gun is constantly getting caught on chairs or rubbing into their hip. Holster design may still have a ways to go.