A Luger is the name of a famous German handgun, used in the 20th Century. The semi-automatic pistol was designed by Georg Luger in the early 1900's from an older gun by adapting it to use the 7.65 parabellum, and then later increased stopping power by moving to the 9mm parabellum.
Asthetically the gun is very different looking, with a normal grip of a modern handgun but with a slimmer barrel like that of a six-shooter, giving it a very distinct, and depending on who you ask, attractive look.
The gun became standard issue for the Germans and Swiss in World War One, but the Germans replaced it for the Second World War. It is often associated with Nazi's, seen in movies like Indiana Jones and the Last Crusade, probably because Lugers were widely used in World War Two even though it was replaced.
Old Lugers are very expensive to attain for gun collectors, but an American company now holds the rights to the gun and apparently produces them for sale.