There is a great write up over at the Firearms Blog detailing the weapons of District 9. Like everything else District 9 actually got the weapons right as well, using proper firearms for the area (South Africa). They also use the weapons in the proper ways. Head over there and take a read, and don’t worry if you haven’t seen the movie the article doesn’t contain any spoilers other than the weapons use.
Seriously this movie has done so much right. It’s truly one of the great science fiction movies of the decade.