User can stack any/all different effects, powers and abilities on themselves, others, weapons and items either to increase their overall effectiveness or grant entirely new powers from the stacked effect. Unlike Power Augmentation the user actually stacks the power or effect itself instead of merely doubling its power, this power can increase all parameters of any ability, power or effect such as range, strength, penetration, radius, targeting, duration, etc.
Using the Kaio-ken Kamehameha, Goku (Dragon Ball series) stacks the power-boosting effects of the Kaio-ken onto his Kamehameha, enhancing the beam's strength.
Goku (Dragon Ball series) stacking the Kaio-ken and his Super Saiyan Blue form.
Fused Zamasu (Dragon Ball Super) creates his Barrier of Light by combining and stacking both sources of his power.
Along with the Shikon Jewel shards to empower his Banryū, Bankotsu (InuYahsa) also made a wish on the halberd to grant it demonic powers should he kill 1000 humans and 1000 demons.
All for One (My Hero Academia) is an ability theft based Quirk that allows its user to steal and stockpile countless Quirks, combining them in various different ways, such as combining Muscle Coiling with Air Pressure and numerous attack power/strength augmentation abilities to magnify its destructive capacity.
Using the Kagutsuchi Chidori, Sasuke Uchiha (Naruto) stacks the black flames of Kagutsuchi with the electricity of Chidori.
Yuri (Final Fantasy: Crystal Chronicles) can stack the effects of his spells not only to increase their range and power, but also generate entirely new spells from stacking.
Samus Aran (Metroid) is able to stack the effects of her various beam weapons…
…such as stacking the Cahrge Beam with Long Beam to increase is duration and strength…
…combining the Ice Beam with the Wave Beam…
…combing the Ice Beam with the Charge, Wide, Plasma, and Wave Beams…
…combining the Charge Beam with the Wide and Plasma Beams…
…or combing the Plasma Beam with the Charge and Wide Beams.
Shujinko (Mortal Kombat series) replicates the combined fighting power of various heroes and villains in his vicinity...
...and uses the stacked power to defeat Onaga.
Ratchet's (Ratchet and Clank series) OmniWrench 10K can modded with the Fire-Bomb wrench mod, Shock Crystal wrench mod, Wild Burst wrench mod, or Triple Wave wrench mod in order increase its power.
During his time in working for MegaCorp, Ratchet was able to to purchase illegal weapon mods for most of his weapons from Slim Cognito, allowing them shock enemies with the shock mods or burn them with acid mods, adding to their already incredible power.
When Ratchet was kidnapped to be a gladiator in Dread Zone, he was able to outfit his weapons with Alpha mods to boost he weapon's speed, knock-back, damage, range, ammo, blast-range, jackpot, and nano-boost, and Omega mods shock, brainwash, napalm, freeze, morph, infect, time-bomb, and mini-bomb effects.
Ryu (Street Fighter series) is able to stack the effects of his electricity ki manifestation with the multi-hitting effects of Shinku Hadoken to create his Denjin Haoken, allowing it to hit enemies up to eight times while also eletrocuting them.
Ken's (Street Fighter series) can manifest his ki in the form of fire and use it to attack with his devastatingly powerful, flaming version of the Shoryuken, the Shinryuken. The attack burns his opponents while also creating a vacuum effect to keep its opponents in range and strike them multiple times.