Dragon Ball is the Trope Codifier. The Super Saiyajin form is famous for giving the character glowing golden hair and a gold Battle Aura. It is later subverted with the Super Saiyajin 4 in GT, as well as Super Saiyajin God in Battle Of Gods.
Especially when Bronze Saints get upgraded Cloths through the blood of Gold Saints. Then this trope is in full effect as their regular armors take a golden shade to highlight their full power.
Karasu from YuYu Hakusho turns his hair golden in the Dark Tournament finals. there have been a few jokes about him turning Super Saiyajin. It's even funnier, considering that his seiyuu and voice actor play Vegeta and Son Gohan, respectively.
Also, Sensui 's Shinobu personality and Sei-Kou-Ki/Sacred Energy. Though it doesn't dye his hair.
Naruto gains this after defeating The Nine-Tailed Fox inside their shared consciousness, allowing Naruto to siphon the Fox's power at will. Naruto later achieves perfect control after making peace with Kurama, allowing the two to work in unison.
Takeru: Zuul! I'll show you everyone's anger! This is the final fight! I'll put everything on the line! (God Mars turns golden while church bells ring in the background.) Takeru:MARS FLASH! (God Mars summons the Mars Flash.) Takeru: FINAL GODMARS! (God Mars performs a vertical slash and jams the Mars Flash into Zuul's gut.)
The first Futari wa Pretty Cure MaX Heart movie had the Golden Power, which turned Pretty Cure and Shiny Luminous' clothes a glowing gold and their earrings and brooches into diamonds. (Subsequent movies featured a different super form.)
The Medicine Peddler of Mononoke has his demon-slaying form, who is robed in gold and covered with golden tattoos. As a bonus, the paper talismans he usually uses are replaced with stronger variations whenever his Super Mode shows up. What color are they? Guess.
The upgraded Goku Uniforms from Kill la Kill have gold accessories instead of silver.
Superman Prime, the being Superman will become many centuries into the future as seen in DC One Million, is completely Gold and is quite possibly Superman's strongest form.
The Sentry, Marvel's pastiche of Superman, whose powers verge on the ridiculous and psychological problems on the tragic.
The goal of The Last Dragon is to achieve this, apparently Bruce Lee was the first to do so here.
Live Action TV
God Ryukendo from Madan Senki Ryukendo. He later gets a second Super Mode called Ultimate Ryukendo that adds even more gold trim. Magna/Ultimate Ryugunou and Ultimate Ryujinou get similar makeovers.
Kamen Rider Kuuga has an interesting spin on this, as later in the series he gains access to the "Golden Power", which beefs up all of his alternate forms into "Rising" versions, giving them some nice gold trim in the process. Kamen Rider Decade takes this a step further, giving Kuuga a Rising version of his original Super Mode Ultimate Form (which already had some gold, but was still primarily black).
Super Sonic from Sonic the Hedgehog. He is admittedly, by word of Yuji Naka, based on Super Saiyan Goku from Dragon Ball. He is obtainable by using all 7 emeralds in conjunction with 50 rings. he becomes invincible and gains the ablity to fly. Several other Super Forms in the series take on a golden hue. This is also his Final Smash in Super Smash Bros. Brawl and is a form of his in the comics and Sonic X.
The Golden Gun from GoldenEye, and the golden Cougar Magnum from Perfect Dark. To a lesser extent, the golden/silver PP7s from GoldenEye as well.
In BlazBlue this happens to Tager in his gag reels, thanks to Kokonoe's modifications.
This may be a reference to its predecessor, the Guilty Gear series, which often included golden-shaded character variants that were extremely overpowered.
In Knights of the Round, Arthur and his friends' armors and swords got bigger and eventually became golden as they leveled up.
Yet another Arthur can don golden armor in the Ghosts 'n Goblins series, greatly powering up his attacks and giving him the ability to cast magic based on his weapon of choice. In his appearance in Marvel vs. Capcom 3, equipping this armor is one of his super moves.
In Wild Guns, when you activate your Limit Break, your character flashes gold.
Subverted in the first Tomb Raider game (and in Tomb Raider Anniversary): if Lara Croft steps onto the Midas Hand, she turns into solid gold and dies.
The Warrior Force spell in Skyblazer does this: it makes you invincible and doubles the strength of your attacks for 5 seconds or so.
In Mega Man X3, X's armor parts can be upgraded further if you find the corresponding chip parts, but normally you can only pick one. If you get the whole armor but pass up the chips, then in the first fortress level you can find a hidden capsule that gives X the benefits of all four chips and more, turning his armor a stunning gold color. The Ultimate Armor in the later games has its own amazing traits, but nothing as absolutely broken as the Gold Armor's combination of two air-dashes, health recovery, a damage-reducing forcefield, and a supply of instant charged shots.
Laguna, in Dissidia 012, uses various weapons in battle. In his EX Mode, they all are colored gold, in reference to the Aura spell in Final Fantasy VIII, which turned the whole character gold.
Front Mission Evolved plays with this. The EDGE System usable by the player gives a silver sheen to Dylan's Wanzer but the system used by Blood Knight Cornelius colors his Wanzer gold. The 'silver = good' and 'gold = evil' is reinforced by on-off ally Adela's EDGE System: When she is an ally her EDGE glow is silver but when she falls under More than Mind Control in the same cutscene it becomes gold, as does Dylan's when his Wanzer gets taken over.
In Tasakeru, Zero's Shogun transformation has a glowing golden aura.
Discussed in Linkara's review of The Technis Imperative. He notes how Teen Titans characters seem to be reincarnated into more powerful golden forms and joked that had Gandalf been a member of the team, he would have resurrected as Gandalf the Gold.
The Golden Kanohi and Golden Armor in BIONICLE. The former gives the wearer the power of 6 Kanohi in one, while the Golden Armor allows to wearer to destroy all solid Antidermis.
Also, in the game BIONICLE Heroes, a Toa's Hero Mode is completely Gold.
In the Adventure Time episode "Power Animal", Jake is empowered by the Party God with the energy of a thousand partying demons to save Finn from the gnomes. His super-mode is a glowing golden-yellow with technicolor stars for eyes, which can be seen in contrast with his typical brownish-yellow when he runs out of steam.
The Transformers has Electrum, a golden liquid with the special property of turning any metal that touches it temporarily Nigh Invulnerable. Transformers augmented by this material will also turn gold until it wears off.