The user can produce/create/generate clothing from energy or matter or drawing them from another dimension. They gain abilities related on the type of clothing worn, although this may be connected to their personal opinions, cultural connections, etc. This may result in the destruction or transformation of their current attire.
...and clads Gohan in training gi similar to Goku's.
Gohan (Dragon Ball Z) can instantly don his Great Saiyaman costume by pressing a button on his Great Saiyaman Watch.
When Prince Adam (Masters of the Universe) wields his sword...
...his clothes become armor and he becomes He-Man
Jaime Reyes/Blue Beetle (DC Comics)
While in his debut Hal Jordan's (DC Comics) Green Lantern costume was just another costume, it was later established that his and the other Lanterns costumes are constructs created by their rings while activated.
Superman's (DC Comics) costume in the New 52 is a biotech armor that allows him to materialize it on his body whenever he wants while wearing it.
Zatanna (Young Justice/DC Comics)
Erza Scarlet's (Fairy Tail) Knight allows her to magically generate different armor and clothing from different dimensions.
Lucy Heartfilia (Fairy Tail) can transfer Celestial Powers to herself and gained a new dress based on each Zodiac Spirit.
Coordinator (Fairy Tail) can use Requip similar to Erza's.
Emi Yusa (The Devil is a Part-Timer!) materializes silver armor on her arms and legs.
The members of Frieza's race (Dragon Ball) are able to grow their own "bio-suits" and remove them at will.
Shinobi (Senran Kagura) can use their stored Yang Energy to manifest of each shinobi's idealized appearance.
Thuries (Valkyrie Crusade) can create clothes that bring happiness to all who wear them.
Spider-Man's (Spider-Man Unlimited) spider-suit is composed of nanobots, allowing him to materialize it around his body at any time.
Rarity (My Little Pony: Friendship is Magic)
Illyria (Angel) manifesting a leather bodysuit.
Cinder Fall (RWBY) woven Dust into clothing
Captain Underpants (Captain Underpants) can conjure up limitless amounts of underwear to fling at his enemies.
Trish (Devil May Cry series)
Sabrina Spellman (The Chilling Adventures Of Sabrina)
Ray Manchester and Henry Hart (Henry Danger/Danger Force) uses special Bubble Gum to transform into their alter-egos Captain Man and Kid Danger