A Stalin organ or multiple rocket launcher. Featured very much in the second world war and was used to help stop the German advance. So called after Joseph Stalin (1879-1953), the communist leader of Russia. The rockets make a whining noise like a church organ when fired.
The guide said that he had one of these firing all night next to his bedroom and that he was unable to sleep.
One of many different types of land mines and for which Cambodia is famous. There are several duds for the tourists to experience walking on. They were laid indiscriminately by the Kymer Rouge to destabilize the government. This warped thinking continues to claim about 75 victims per month, down from 300. There are many people walking around on crutches with only one leg. The British SAS had a camp in Malaysia where they trained Kymer Rouge soldiers in land mine techniques. The Kymer Rouge were allies in a way against the communist Viet Cong. Yet more warped thinking. Only two years ago two tourists, small boys, were killed when they went behind some bushes for a pee. Better to forget your modesty and pee on the path. Even some areas of Angkor Wat national park are still dangerous.
The guide with a machine gun on a tripod, probably a 7.62mm general purpose machine gun.
There are clear signs saying do not touch but everybody wants to pose as Rambo with an M60 machine gun. Yes they have got the lot, M16, M60, Armalite, AK47 etc .