[[quoteright:204:[[Franchise/{{Pokemon}} http://static.tvtropes.org/pmwiki/pub/images/009Blastoise_6911.png]]]]

The AmmunitionBackpack is cool and all, but having to lug both it and your gun may be a hassle. Why not combine them both and get yourself a Backpack Cannon! Yeah, it would probably be really hard to aim, but come on.

Compare ShoulderCannon, WeaponizedAnimal, JetPack, and WeaponizedExhaust.
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!!Examples:

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[[folder:Anime and Manga]]
* General Catton in ''SamuraiPizzaCats'' had a double backpack cannon.
* Throughout the Franchise/{{Gundam}} franchise, there have been several examples.
** The [=GM=] Cannon 2 from ''Anime/MobileSuitGundam0083StardustMemory'' features a double backpack cannon. Its predecessors, the [[Anime/MobileSuitGundam Guncannon]] and original [=GM=] Cannon, had [[ShoulderCannon shoulder-mounted cannons]].
** From the same series, there's the Xamel and it's folding {{BFG}}. It's a bit hard to tell if it is this or a ShoulderCannon since it's not entirely clear given the Xamel's unusual shape, but as far as anyone can see it's actual shoulders are bare.
** The Zaku Cannon, introduced in [[AllThereInTheManual Mobile Suit Variations]], was found to be unstable due to its backpack being too heavy and the recoil being too great, though some units were later used by the Earth Federation in ''Anime/MobileSuitZetaGundam'', and by Zeon remnants years later in ''GundamUnicorn''.
** The [=RX-78-01=] from ''Gundam: The Origin'' had a backpack-mounted cannon and one [[LaserBlade beam sword]] rack, instead of the traditional pair of saber racks. The [=RX-78-02=], Amuro's Gundam, could have one of the racks replaced by a similar cannon.
** The [=OZ-07MS=] Tragos from ''Anime/MobileSuitGundamWing'' featured a backpack cannon and a hoverskirt that made it resemble the original Guntank, although both could be detached to allow the Tragos to function as a conventional mobile suit as well.
** ''Anime/AfterWarGundamX'': The titular Gundam features the backpack-mounted [[WaveMotionGun Satellite Cannon system]]. Its MidSeasonUpgrade, the [[MeaningfulName DoubleX]], naturally has twin cannons.
** The Doppelhorn Striker Pack from ''GundamSeedDestiny'' is basically this. It isn't seen too often, but can be attached to any Striker-capable Mobile Suit (such as the standard-issue 105-Dagger).
* The [[CodeGeass Lancelot Conquista]]'s main weapon is the large [[WaveMotionGun Hadron Blaster]] on it's back that folds forward and docks with the [[{{BFG}} VARIS rifle]] in order to fire. And it's so freaking powerful that nothing [[LensmanArmsRace except the Guren SEITEN's upgraded radiant wave surger]] can stop it.
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[[folder:Comic Books]]
* In ''ComicBook/TransformersLastStandOfTheWreckers'', Ironfist's lightformer cannon ''is'' his backpack... but he has to take it off to use it.
** The tank mode turret of Ironfist's teammate Guzzle is situated on his back when in robot mode, with the barrel extending far past his head.
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[[folder:Film - Live Action]]
* From ''Franchise/StarWars'', Boba and Jango Fett's {{Jetpack}}s can fire rockets.
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[[folder: {{Literature}}]]
* The ActionPrologue of Creator/RobertAHeinlein’s ''Literature/StarshipTroopers'' features “Y-racks” on the PoweredArmor. They launch pairs of HE bomb a few hundred yards to the left and right. The mission was to just smash stuff, so there was no need to aim.
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[[folder:Tabletop Games]]
* ''TabletopGame/{{Shadowrun}}''. The Ballista Multi-Role Missile Launcher, which is worn as a backpack.
* ''Battlelords of the 23rd Century''. The Cizerack (large quadrupedal catlike aliens) have been known to wear weapon systems mounted on their backs. See a picture [[http://tinyurl.com/34otgrn here]].
* Likewise ''Battle Cattle'' (pic [[http://tinyurl.com/3xryles here]]).
* Most of the power armor in ''{{Rifts}}'' has this, notably the Glitterboy and its variant armor.
* In ''TabletopGame/{{Warhammer 40000}}'', the Tyranid Biovore is a [[NaturalWeapon living]] BackpackCannon.
** Tau battlesuit jetpacks have mounting points for either support systems or weapons, with missile launchers most commonly shown in GW's in-house models fitted to the jetpack. The old Broadside models had the best demonstration of this in the franchise; their backpacks were fitted with a pair of railguns, which are [[{{BFG}} at least twice as long as a man is tall]] - one on each shoulder.
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[[folder:{{Toys}}]]
* ''Franchise/{{BIONICLE}}'': the Toa Hordika's Rhotuka Spinners.
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[[folder:Video Games]]
* Mario's F.L.U.D.D. in ''VideoGame/SuperMarioSunshine''
* The Buster Pod from ''VideoGame/CustomRobo Arena'', which was just a cannon mounted on your robo's back.
* ''VideoGame/PokemonBlackAndWhite'': [[WeaponizedAnimal Genesect]], a Pokémon with a mounted cannon on its back, as modified by Team Plasma.
** Blastoise from [[VideoGame/PokemonRedAndBlue Gen I]] is a giant turtle with two cannons in its shell! Its SuperMode introduced in ''VideoGame/PokemonXAndY'' changes it to one large cannon while giving it two [[ArmCannon arm-mounted cannons]].
* Carol from ''VideoGame/{{Wild ARMs 5}}'' uses a backpack-mounted missile launcher. She can't use it without falling on her ass, but it does pack quite a punch.
* The Taraba ninja from ''VideoGame/{{Shinobido}}'' use these as weapons. [[HighlyVisibleNinja Yup, cannons, right...]]
* [[http://megaman.wikia.com/wiki/Shadow Shadow]] from ''VideoGame/MegaManXCommandMission'' has a "Pulverizer Cannon" on his back. It takes three turns to [[ChargedAttack charge]], and like its name suggests, it hurts ''a lot'' on all your characters.
* The Dwarf from ''VideoGame/{{Sacred}}'' has this as a special weapon.
* In ''VideoGame/StarCraftII'', the Thor [[HumongousMecha superheavy siege walker]] and its SuperPrototype Odin both feature a set of four backpack-style guns, described as [[{{BFG}} 330mm high-ex cannon]] (you could fire a smallish ''person'' out of a gun like that). While they are used for single salvoes rather than being an alternate mode shift like the Siege Tank, the mech still has to hunch back and take up a firing stance, rendering it briefly immobile while the weapons are being fired. The results are usually [[NoKillLikeOverkill worth the hassle]].
* {{Game Mod}}s for ''{{VideoGame/Tribes}}'' usually add at least one of these. Instead of carrying around a regular backpack, like a shield pack, you can stick a big gun on your shoulder, allowing you to use both your hand weapon and the backpack weapon at the same time.
* The ''VideoGame/DukeNukem3D'' boss "Overlord" has a back-mounted rocket launcher.
* Seeing as the class is a straight-up {{expy}} of [[Franchise/StarWars Boba/Jango Fett]], Bounty Hunters in ''VideoGame/StarWarsTheOldRepublic'' have an attack or two that launches rockets out of their jetpack.
* In ''VideoGame/KaijuCombat'', the [[AIIsACrapshoot S.C.U.D.]] attached to the {{kaiju}} Katyusha is one that can twist around and serve as a {{jetpack}}.
* In ''VideoGame/DarkVoid'', your jetpack has guns in it. Sort of justified in that they only get used in flight mode when they can be aimed.
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