The South African Denel NTW-20 is a 20mm rifle that was used by MNU forces in District 9. In the movie it appeared once where an MNU officer shot Wikus while he was in the Prawn-designed exo-suit, it did massive damage to the suit and blew a big hole in it's back. The weapon is a big bolt action rifle that fires a massive 20×83mm round and has a 3 round box clip.
The Denel NTW-20 is a South African anti-materiel rifle or large-calibre sniper rifle, developed by Denel's Mechem division in the 1990s. The weapon was designed by Tony Neophytou (co-designer of the innovative Neostead combat shotgun) and intended for deployment against a wide variety of targets, including parked aircraft, telecommunication masts, power lines, missile sites, radar installations, refineries, satellite dishes, gun emplacements, bunkers and personnel, using a range of specialized 20mm and 14.5mm projectiles. As with other weapons of this type, it can also be used for counter sniping and ordnance disposal (shooting explosive ordnance from a safe distance).