The Shoulder Cannon (also known as the Plasmacaster) is the Predator's main ranged weapon that usually sits on the left shoulder. It fires a powerful plasma blast that varies in strength. Many variants of the Shoulder Cannon exist, with almost every Yautja having a unique one. Here is an overview of the capabilities and the different types of shoulder cannons and plasmacasters.
Classic Predator Shoulder Cannon
The classic shoulder cannon was the Jungle Hunter's most recognizable weapon besides the wristblades. The weapon shot blue "bolts" of plasma and drew power from the power back behind the left shoulder of the Predator, the same that was used for the cloaking device. The Jungle Hunter Predator killed Blain, Mac, and Poncho with the shoulder cannon, and wounded Dutch in the arm. The shot that disabled Dutch's M16 was most likely a lower-powered one, either meant to decapacitate him, or the shoulder cannon was low on power. When dueling with Dutch, the Jungle Hunter dropped the shoulder cannon to level the odds, in accordance with his hunting rules. Although dropped in a small lake, the classic shoulder cannon was destroyed when the Predator activated his self-destruct.
The Predator's shoulder cannon is connected to a laser targeting system usually located on the right side of the bio-mask, while the plasmacaster itself is on the left. The red three-dot laser pointer is an iconic feature of the Predator and helps the targeting to track its prey. Similar to the one-dot pointer of modern weapons on Earth, the three dots might help with three-dimensional tracking. A small weakness of this system is that an enemy might notice the three dots and move out of the way. Mac saw them at the last moment and was a bit mystified by the laser, and failed to react.
The shoulder cannon also interfaces with the Predator's vision mode, provided by the bio-mask or enhanced eyesight in the case of Upgrade Predators. In addition to the three red dots that anyone can see, a rectangle appears on the Predator's selected display mode, which is most commonly thermal vision. The triangle tracks the target across the landscape, while any new targets get highlighted as well, accompanied by a whooshing sound. The unleashed plasma bolt will then move toward the target, however, it is not homing like the smart disc. The Predators use many different vision modes, with thermal vision and Xenomorph vision used mostly for combat, while the others are more useful for tracking prey or traversing the environment.
City Hunter's Shoulder Cannon
The City Hunter from Predator 2 had much more gadgets and weapons than the Jungle Hunter, including a different type of shoulder cannon. The bronze design of the City Hunter armor and equipment was influenced by the Samurai, and some of the tech resembled fish scales, which is similar to both the Jungle Hunter's and Lost Tribe's ships. The bronze shoulder cannon itself was flat, making it slightly smaller, and had two orifices instead of one. Dissimilar to the Jungle Hunter, the City Hunter had no big bulge behind the shoulder cannon, which is where the power source was supposed to be. The City Hunter used the shoulder cannon less than the Jungle Hunter and relied on the disc, spear, and speargun more.
Greyback Elder Shoulder Cannon
Although in the same clan as the City Hunter, the Greyback Elder Predator employed the same kind of shoulder cannon as the Jungle Hunter, although with an important difference. While almost all Predators have the laser targeting on the bio-mask, Greyback had it straight on the shoulder cannon. Perhaps the filmmakers wanted to have the dramatic effect of the three laser dots but did not want to create another unique mask for the elder. It is also possible that most shoulder cannons have this feature, but the bio-mask laser takes preference, as it provides targeting for other weapons as well. Greyback also had a big bulge behind the left shoulder, just like the Jungle Hunter.
Super Predator Shoulder Cannon
The Super Predators were slightly more technologically advanced than the previous Yautja seen in the movies, with new vision modes, a better cloak, and a new type of shoulder cannon. The shoulder cannon had three smaller components that rotate in opposite directions, producing a powerful plasma blast, although, it can be varied in strength. The Tracker Predator shot Ronald Nolan to pieces, but moments later blasted a hole in the chest of Nikolai. The hole was smaller than the one that the Jungle Hunter shot through Blain in the first movie. Later on, the Berserker Predator fought the Captive Predator and rapid-fired his plasmacaster, but was unable to make significant damage as he always narrowly missed.
Young Blood Predator Shoulder Cannon
For the Young Blood Predators from Alien vs. Predator, the gaining of the Shoulder Cannons was a part of their blooding process, and they did not start their hunt with these weapons. The three plasmacasters were placed deep inside the pyramid under the Antarctica ice, and they had to fight through humans and Xenomorphs to reach them. The weapons looked slightly different but similar to the classic shoulder cannon of the Jungle Hunter, while Scar Predator's plasmacaster was the largest one. Scar was the only Predator who reached the plasmacaster - he gained it from Alexa Woods and immediately put it to use against a horde of Xenomorphs. Later on, he lost it again, just before escaping the self-destruct blast of the pyramid on the automated sled. The plasmacaster would have been very useful in the fight against the Alien Queen, however, as seen in AvP Classic, the Predators sometimes disable their plasma weapons on purpose when fighting her, for gaining maximum honor.
Double Shoulder Cannons
Somes the Predators resort to using two shoulder cannons at the same time, as Wolf Predator did in Aliens vs. Predator: Requiem. Realizing the presence of the dangerous Predalien, Wolf grabbed a second plasmacaster from a fallen comrade in the crashed Predator scout ship. Fortunately for Wolf, his armor supported another "arm" for the other plasmacaster and his targeting had no trouble with it. On regular hunts, this type of setup might be forbidden, but Wolf needed the extra firepower and used it for great effect both in the sewers and on the streets of the city of Gunnison.
The Dual shoulder cannon setup was not the only configuration of the plasmacaster that Wolf used. He later combined the two shoulder cannons into one powerful plasma pistol, where the second caster became the handle. This plasma pistol fired slower but more destructive blasts, able to vaporize opponents completely. However, the pistol later fell into human hands, which used it against Xenomorphs and escaped from the Gunnison city nuke in a helicopter. Finally, the pistol reached the desk of a mysterious lady Yutani, hinting at a Weyland-Yutani merger and the Predator technology being used to develop the company's interests.
Fugitive Predator Shoulder Cannon
The Fugitive Predator and his clan from The Predator used even more advanced technology than the Super Predators, even employing some nanotechnology. Distinct from all the Predators before him, the Fugitive Predator wore the shoulder cannon on his right shoulder. However, he lost most of his gear just before being captured by Stargazer, including his shoulder cannon and bio-mask. During his escape from the lab, he gained another bio-mask and the same type of advanced shoulder cannon, belonging to another Predator who Stargazer captured some time before. The exploits of this other Predator are described in The Predator: Hunters And Hunted prequel novel, one of the best Predator books.
The Fugitive Predator's bio-mask held another small plasmacaster, hidden in a small compartment on the right side, next to the three-dot laser pointer. This tiny weapon was employed automatically in some situations, protecting the bio-mask's wearer. For example, when Rory McKenna wore the mask on Halloween and he was attacked by a random local, the mask retaliated by blowing up the house of the attacker. The existence of this powerful weapon begs the question, why would the Predator even need the classic shoulder cannon anymore, and why wasn't this small plasmacaster used in more situations.
Shoulder Cannon With Human Interface
While the Fugitive Predator mostly used the shoulder cannon taken from the glass display in the Stargazer lab, the humans still held on to his original plasmacaster. Will Traeger, the head of the Stargazer project, employed the shoulder cannon in the field by himself, plugging it into his neck with a human interface. It is interesting that he was able to use the cannon as well as he did without a bio-mask. It was possibly linked to his eye retinas somehow, similar to how the Assassin Predator's vision mode worked. However, Taeger did not have much luck with the cannon, as a minor distraction caused the cannon to turn towards his head, and blow it off.
Predator Killer Shouldercannons
The Predator Killer suit employed nanotechnology (expanding out from a small gauntlet like an Iron Man suit) and used a ridiculous amount of shoulder cannons, totaling at least eight. It had three tiny plasmacasters on each shoulder (similar to the one inside the Fugitive Predator's bio-mask) and two gigantic ones expanding outwards. In addition, each shoulder cannon seemed to have its own targeting laser, making the whole suit light up like a Christmas tree. This seemed like overkill, and the tiny cannons would have probably been enough as the bigger casters would severely limit the suit's mobility. Although the Predator Killer suit was the Fugitive Predator's gift to humanity, it was never seen in action and probably never will be.
Heavy Plasma Cannon
The Predator Killer suit wasn't the only instance when the Yautja employed a huge plasmacaster, the Yautja military castes heavy weapons as well. In the Aliens vs. Predator: Duel comic, a Predator was fed up with their losses against the Colonial Marines and grabbed a heavy plasma cannon. He then proceeded to destroy the Colonial Marine landing craft, stranding the survivors on the planet. Although this weapon wasn't necessarily attached to the shoulder of the Predator, it was still an impressive and powerful plasmacaster. The cannon wasn't interfaced directly with the bio-mask and had its own scope, similar to the Colonial Marine SADAR rocket launcher.
Hunting Grounds Plasmacaster
Not surprisingly, the shoulder cannon shows up in all the Predator games, including the Alien vs. Predator ones. It is also an integral part of the latest Predator game, Hunting Grounds, where a common strategy for the Predator is to stay in the trees and wear down the fireteam with constant shoulder cannon blasts from the branches. Although the game offers many customization options, the shoulder cannon stays mostly the same, with the default one looking like the original Jungle Hunter plasmacaster, but a bit smaller and round. Most of the Predator types mentioned above are also presented in the game, with their distinct shoulder cannons. Like in the movies, the shot can be charged up and draws power from the same source as the cloak.
Hand Held Plasma Caster
Finally, Predator: Hunting Grounds presents another type of plasma pistol (named "hand-held plasma caster"), distinct from the one that Wolf combined from two separate plasmacasters. This is an optional weapon but turns out to be one of the best ones in the game. The main advantage is that it does not alert your enemies with the laser sight and does not draw power from the cloak. It deals a fair amount of damage and is a bit slower than the regular shoulder cannon. A pistol also shows up in the older Alien vs. Predator games, but shoots an electrical charge and cannot be considered a plasmacaster.
In conclusion, the shoulder cannon is one of the best Predator weapons and a good companion to the wristblades. Many types of it exist, but most of them sit on the left shoulder of the Predator and shoot out a powerful plasma blast, which can vary in strength and speed. The weapon is connected to the targeting display of the Predator's bio-mask and the shot can be targeted both with a three-dot laser pointer and targeting rectangle in the vision mode. The plasmacaster is present in all Predator movies (except Prey) and most of the Predator games and comic books.