Seen mounted on the back of a hummer used by escaped convicts. You get to use it once you disable the hummer.
Barrett M82A1
A Barrett M82A1 is used by Carlito Keyes and his sister. The rifle is the M82A1 model, equipped with the accessory rail of an M82A1M (without the back-up front sight). This weapon is not usable by player.
Found in gunstore and carried by the hunter family. It is equipped with a scope.
Hybrid Assault Rifle w/M203
A rifle that resembles US Army's famous Colt M4A1, although in-game its official name is never claimed however it features differences, such as SA80-like handguard with rails and an FN FAL-style stock.
Used by the special forces team and a survivor. Seen attached with an M203 (which seems to be only for decoration), the player gets to wield it later in the game. It has a capacity of 150 rounds.