Ragtag (Static Shock) can give powers to others, but they are only temporary.
Upon arriving on Earth, Akuro (Alive: The Final Evolution) granted many humans special powers, at the cost of including suicidal urges that most find hard to resist.
The Darkness (Stupid Mario Brothers)
The First Evil (Buffy the Vampire Slayer) merges with Caleb to grant him superhuman strength and durability.
Mata Nui (Bionicle) gave his fellow Glatorian warriors elemental powers of fire, water, and wind
Kagura Tennōzu (Speed Grapher) carries a virus that can be transmitted to grant people's desires
Harimon (Krystalia) has the power to bestow powers to others using the power of his red stones.
While under a blue sun, Superman (DC Comics) develops "Superman Vision" that enables him to grant Kryptonian powers to others...
...as demonstrated here on Jonathan Kent.
When Alex (Misfits) took ecstasy, the powers he took will be given to the person he had sex with, similar to Seth, but, he gives all the powers he took away.
Mikan Sakura (Gakuen Alice) can insert Alices at will.
Cain (Supernatural) transfers the Mark of Cain to Dean Winchester, granting him Demonic Power Immunity and the power to wield the First Blade.
The Formula (Heroes)
Devil Fruits (One Piece)
Onomatopoeia's (Valkyrie Crusade) words can give power.
The Darkness (Skylanders) can grant dark powers to it's followers.
An Space-Time Feather (Valkyrie Crusade) can grant time-traveling powers.
With the power of the Butterfly/Moth Miraculous, Hawk Moth (Miraculous Ladybug) has the power to turn others into supervillains, bestowing on them an arsenal of unique superpowers.
Puppeteer (Miraculous Ladybug) is able to possess anyone who's doll she possesses. Should the doll be of a purified supervillain, they regain their villain identity along with their powers.
Him (Demashita! Powerpuff Girls Z) is able to create black dust, a mass of evil particles that are able to turn normal people or objects into supervillains, along with their own set of superpowers and persona.
Enrico Pucci's Stand, Whitesnake (Jojo's Bizarre Adventure) can remove the Stands of others, storing them in discs. It also makes it able to bestowal these Stands upon others by inserting the discs on them.
Each of the twelve talismans (Jackie Chan Adventures) grants the user a power stolen form the Noble Animals.