Nomads are large, slow-moving Bandits that sometimes carry a large shield, effectively cutting down the damage done to them. Since they move so slow, they are easy targets, but they can take a lot of punishment, making it vital to shoot their head for critical damage.
A variation of the Nomad is the Nomad Torturer, who has a Midget tied to their shield. Shooting the chains off will release the Midget, who will then turn on the Nomad, making a nice distraction while you can sneak behind the Nomad to bypass its shield. The Midget will turn on you after the Nomad is dead.
Another variation of the Nomad is the Nomad Pyro. At longer ranges, it will use an assault rifle, like other Nomads, but at close range, it uses a flamethrower. It has the same weakness as other Nomads, but it has an additional weakness with the fuel tank on its back.