Annihilation is a 2018 sci-fi horror movie staring Natalie Portman, Jennifer Jason Leigh, Gina Rodriguez, Tessa Thompson, Tuva Novotny, and Oscar Isaac. The movie follows Natalie Portman's Lena, who joins an all-female scientific team as they are sent into "The Shimmer", a mysterious energy field surrounding Blackwater National Park which has swallowed numerous expeditions. The film is loosely based on Jeff VanderMeer's book of the same name, part of his "Southern Reach" trilogy.
The following weapons were used in the film Annihilation:
Government agents who detain Kane (Oscar Isaac) carry Heckler & Koch MP5A3s with railed hardguards and Surefire M900 flashlight forgrips
Heckler & Koch MP5K
One of the govenment agents who detain Kane carries a Heckler & Koch MP5KA1 (or A5) with a PDW stock
Rifles
M4A1
The team, including Lena (Natalie Portman), are issued M4A1s for their mission into "The Shimmer". These carbines are fitted with MAGPUL handguards, buttstocks, and magazines.
FN SCAR-L
Kane (Oscar Isaac) carries an FN SCAR-L in a photograph of his time as a soldier.
M16A2
M16A2s carried by a previous expedition are seen in the Fort Amaya mess hall and in the Lighthouse with the rest of Kane's (Oscar Isaac) gear.
Machine Guns
M240B Machine Gun
Anya (Gina Rodriguez) recovers a M240B left by a previous expedition from the Fort Amaya mess hall, but rejects the 28lb weapon as too heavy to carry and leaves it behind.
Other
Barrett M82
A Barrett M82, seen in the watch tower, is among the weapons left behind by previous groups,
Incendiary grenade
Kane (Oscar Issac) and Lena (Natalie Portman) both use some sort of incendiary grenade in the Lighthouse. Kane describes it as a "phosphorus grenade" in his video. Note that the prop appears to be a law enforcement market (i.e. not military issue) smoke grenade with a bare-aluminum body and painted yellow ring (indicating yellow smoke), not a white phosphorous grenade.