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 users are actually stacking 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.
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.
When in the Six Paths Sage Mode, Naruto Uzamaki (Naruto) can stack the power of his Rasenshuriken with the specialchakrapropertiesoftheninetailedbeasts, allowing him to create his Sage Art: Super Tailed Beast Rasenshuriken.
Using the Kamui Lightning Cutter, Kakashi Hatake (Naruto) stacks the space-time properties of Kamui onto his Lightning Cutter.
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.
By pressing different button combinations on his Power Bands, Space Ghost (Space Ghost) can stack his various different beams.
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.