In the third-tier 'dream world' the Wiseman (Scott Glenn) presents Baby Doll with her weapons, one of which is a nickel plated engraved M1911A1 pistol with spare magazines (and small jewelry attachments). In the real world, a blued M1911A1 is used by Baby Doll (Emily Browning).
Baby Doll (Emily Browning)uses a suppressed Heckler & Koch MP7A1 with a tiny red dot sight, a flashlight, and two magazines taped together during the assault on the dragon's lair.
An M4A1 with rails, a SureShot reflex sight, and a flashlight is used by Sweetpea (Abbie Cornish), fitted with a suppressor during the hunt for the dragon's baby.
In the battle with armed automatons, Sweetpea (Abbie Cornish) uses a tactical Remington 870 Shotgun with surefire light, door breaching muzzle, and Blackhawk M4 style stock.
In all of the missions in the dream, Rocket (Jena Malone) carries Heckler & Koch UMP-45 with a SureShot reflex sight, a foregrip, and a flashlight. It is suppressed during the mission into the Dragon's lair.
During the trench battle with the World War One German Zombie Soldiers, Rocket (Jena Malone) uses a combination of bayonet and single shot flintlock pistol. She uses the pistol as a club in hand to hand combat, which is probably the most practical use for the antiquated weapon in that battle.
Blondie (Vanessa Hudgens) use a Daewoo K3 light machine gun fitted with a rail forearm and vertical grip (standing in for the FN Minimi SPW). It is recognizable as a K3 due to the shape of the gas tube and front site, visible in the second screencap below. Despite being seen firing it in the trailer, she abandons it for her MP5K as soon as they reach the trench.
Amber uses either a Glock 17 or 19 as her sidearm. As she seems to always be the pilot in the group, she most likely wouldn't need anything more that this.
The Wiseman (Scott Glenn) uses an anachronistic 03A4 Sniper rifle in the trenches of World War 1, when he explains how the Germans are reanimating their dead with clockwork mechanisms and steam.
A Browning M1919A4 is seen being chambered by Blondie (Vanessa Hudgens) in the air battle with the dragon before the dragon swallows the tail section of the plane.
In one of many (intentional) weapon anachronisms, a zombie German World War One Soldier attacks Blondie (Vanessa Hudgens) in the trench with a rifle that has its bayonet mounted. German soldiers from WW1 would be issued the Mauser Gewehr 1898 rifle, but this is too short to be even the anachronistic Karabiner 98k.
In the battle with the robots, who are guarding a bomb on a train heading for a city, we see energy weapons which look like they may be based on real world guns.
