"A curtain of death raining from the sky. So many bullets at a time your eyes can't keep up."
― Bullet Hell
"Plus, to add insult to injury, in most Japanese shooters I've seen, they also like to put you through what's called "bullet hell." "Bullet hell" is when they throw so many shots on the screen to try and kill you in one hit; they're basically just trolling you to try to get you to die and stop playing."
― Ross Scott/Accursed Farms on most games made from Japan. (Ross's Game Dungeon: Tyrian)
The user can summon a stream of endless waves (ranging from hundreds to thousands to millions) of objects like blades, bullets, energy blasts, etc., around their target to bombard them from all sides with no hope of escape. Users most likely have a complex strategy and pattern to confuse their opponent and limit their movement.
Divine Beasts (The Legend of Zelda: Breath of the Wild)
Heaven Piercing Sword (Sword Art Online); via Release Recollection
Kaname Tōsen (Bleach) using Suzumushi Nishiki: Benihikō to generates hundreds of blades, raining them down to cause heavy damage.
Uryū Ishida (Bleach) using Licht Regen to fire a devastating volley of innumerable arrows down on his target.
Coyote Starrk (Bleach) using Cero Metralleta to fire massive waves of energy bullets, making it hard to avoid.
Lille Barro (Bleach) firing a large barrage of spatial bullets via his "The X-Axis".
Joanna Wise (Buffy the Vampire Slayer Season 11) using the Rain of Death spell to fire off numerous magical bullets.
The One Being Sought (Code:Breaker) using "Deep Presser" to fire off a large amounts of spatial blasts.
A Level 4 Akuma (D.Gray-man) turning its arms into Gatling guns that fires deadly Dark Matter blood bullets.
Rakanoth (Diablo) can fire off a volley of energy blades.
Vegeta (Dragon Ball Z) uses the Continuous Energy Bullet attack so often that Goku once explicitly called the move his technique.
Frieza (Dragon Ball Z) using the Crazy Finger Beam to project rapid-fire energy blasts, too fast for Piccolo to react or avoid...
...and the Barrage Death Beam to project rapid-fire Death Beams.
Super Buu (Dragon Ball Z) using his Human Extinction Attack, firing a massive barrage of ki bullets to wipe out the majority of Earth's population.
Son Goku (Dragon Ball Z) using the Continuous Kamehameha to fire multiple rapid fire Kamehameha Waves.
Gotenks (Dragon Ball Z) using Continuous Die-Die Missiles to launch an intense barrage of ki bullets, enough to shatter Earth.
Dr. Kochin (Dragon Ball Z: the World's Strongest) using his Vulcan Cannon to fire a massive barrage of bullets that forced even Krillin on the run.
Using his Blaster Meteor, Broly (Dragon Ball Z: Broly - The Legendary Super Saiyan) vents out his excess energy by unleashing a barrage of homing energy balls.
Goku Black (Dragon Ball Super) preparing a rapid-fire variation of his Black Power Ball.
Kenshiro (Fist of the North Star) uses Tenkai Senretsu Shō to project a large barrage of Tōki spheres.
Destructor (Futurama) firing an arm-installed Gatling gun, letting loose a barrage of bullets.
When Sesshōmaru (InuYasha) first acquired Tōkijin, he developed a Kenatsu that fires barrage of demonic energy needles.
Inuyasha (InuYasha) firing burst of Adamant splinters with the Adamant Barrage...
...and unleashing the Meidō Zangetsuha as a barrage of dimensional blades that tear apart enemies and banish them into the netherworld.
Xigbar (Kingdom Hearts) can shoot multiple bullets, even summon them out of nowhere to catch an enemy by surprise.
Xemnas (Kingdom Hearts) surrounds his enemies with a massive amount of Ethereal Blades for his ultimate attack.
Tenten (Naruto) rapidly summoning her weapons from her scroll.
Sasuke Uchiha (Naruto) using his Chidori Senbon to create a widespread of multiple electric needles.
Jiraiya (Naruto) using Sage Art: Hair Needle Barrage to fire his hardened hair in a massive barrage of needles.
Naruto Uzumaki (Naruto) using Sage Art: Massive Rasengan Barrage to rain down a barrage of multiple Senjutsu-enhanced Rasengan, powerful enough to stun even Kurama/Nine-Tails.
Obito Uchiha (Naruto) channeling Wood Release: Cutting Technique through the Ten-Tails to fire devastating and impossible to dodge attacks.
By swinging his rod, Urashiki Otsutsuki (Boruto: Naruto Next Generations) uses Amenosubaruboshinomikoto that can launch a large barrage of chakra hooks at his enemies.
Sakazuki (One Piece) raining his Ryusei Kazan, a barrage of magma fist bullets, causing massive and widespread damage.
Borsalino/Kizaru (One Piece) raining his Yasakani no Magatama, a barrage of destructive photon bullets causing massive devastation.
Arceus (Pokémon) unleashing his Judgement attack.
Tasha Godspell (Witch Hunter) unloading his Dimensional Gallery to create a battlefield of raining bullets.
TM-1 Launcher Spider (Yu-Gi-Oh!) firing a large barrage of missiles onto a single target accurately.
Yusuke Urameshi (Yu Yu Hakusho) using the Spirit Shotgun to scatter his Spirit Gun bullet into a barrage of bullets.
Younger Toguro (Yu Yu Hakusho) flipping his finger rapidly to launch a barrage of vacuum bullets at Yusuke.
Wall Eehto (Fairy Tail) firing numerous magic bullets that cover a large area at a rapid firing rate.
Acnologia (Fairy Tail) casting Eternal Flare firing starry lights in the sky which rains down in a massive radius with destructive force enough to destroy numerous towns.
Clownpiece (Touhou Project) firing multiple lasers and stars
Ryu (Ninja Gaiden) when he cast the Wind Blade Ninpo at full power can create a storm of air blades that decimate his enemies.
Kavaxas (Teenage Mutant Ninja Turtles 2012) unleashing a barrage of laser beams from every fingertip.
Capone Bege (One Piece) houses numerous artillery such as cannons in his dimensional fortress which can be volley fired at the enemies.
Admiral Fujitora (One Piece) can levitate massive amount of rubble and rain them down to sink an entire fleet of battleships.
Kurumi Tokisaki (Date A Live) can use the guns of her time clones to volley fire at her enemies.
Misha Kreutzev (Toaru Majutsu no Index) can unleash Command Sweep after using Magic Circles in the sky, turning each star in the sky into tens of millions of arrows of fire that rains down at the enemy.
Delsin Rowe (Infamous: Second Son) using Radiant Sweep to unleash a barrage of neon energy bolts.
Hoshizora Miyuki/Cure Happy (Smile Precure) unleashing a massive rain of multiple light beams with her Happy Shower Shining attack.
Hajime Nagumo (Arifureta Sekai Saikyou) wielding his Metzelei, a technomagical gatling gun that can rapidly fire twelve thousand bullets per minute to decimate entire armies.