Concept Album: Every non-compilation album, as well as singles. Even his concerts are designed to be visual interpretations of his albums and singles, if not a continuation of their story.
Everything Is an Instrument: The song "4th" consists entirely of gun fire, radio static, explosions, helicopter noise, Gackt singing gibberish in a soprano-like falsetto, and a guitar rhythm. It's surprisingly good.
Epic Rocking: Cube, Birdcage, Blue, Uncertain Memory, Dybukk, Secret Garden and many others.
Genre Shift: Gackt's early albums (and recent singles) tend to be a music version of this. A single album can have a combination of rock, pop, techno, ska, rap, r&b, metal and whatever else Gackt feels at the moment. Even singles will often have contrasting songs on them.
Genre Roulette: Gackt is a rock artist, but what genre of music is going to be on his albums and singles is random at best. Some songs such as Cube, Oasis, Uncertain Memory and Secret Garden don't even resemble any discernible genre. Songs like these are simply referred to by fans as Gackt rock.
Intercourse with You: "Koukuma Heaven", "Vanilla", and "Dispar" are explicit. "Papa Lapped a Pap Lopped" and "Speed Master" are more ambiguous.
Neoclassical Punk Zydeco Rockabilly - Many of his songs, especially "Dybbuk", "Lost Angels", "Memories" and "Ghost". In recent interviews he's even talked about taking this further by combining rock, classical European, traditional Japanese and various other Asian music styles in his newer work.
Vanilla live is the most famous example. But Kagen no Tsuki, Jougen no Tsuki, and Drug Party had plentiful amounts of this as well.
Gackt's second Yellow Fried Chickenz tour has taken this to the extreme with fans encouraging him by throwing underwear, hand cuffs, and whips on stage for Gackt and his band to play with.
Kill 'Em All: "Diabolos" and "Requiem et Reminiscence II" ends with all the characters dying.
Last Stand: His 2005 concert "Diabolos" opens with a scene showing 5 warriors riding into battle with a legion of Darts. Gackt's character wakes up as a superempowered vampire, and is the last man standing.
Ninja: During the song Luna he often has people dressed as these come on stage and fight him. I kid you not.
Ninja Pirate Zombie Robot: The stories in his music contain many of these, such as Cyborg Nazis and Vampire Knights. His concerts can also be said to be this, since they're designed to be combination's of rock concerts, movies, and musicals. This also applies to Gackt himself who is a singer, songwriter, actor, writer, fashion designer
Science Is Bad: Subverted by the Ghosts, soldiers and war prisoners turned into cyborgs by Nazis to be mindless weapons of war turn against their evil creators and heroically sacrifice their lives fighting the Nazi agenda.
Defictionalization: Kamui Gakupo is a vocaloid created by Kentaro Miura (better known for his work on Berserk) based on voice samples from Gackt. Video site Nico Nico Douga once held a vocaloid contest hosted by Gackt were he would sing the winning songs, which used Gakupo as the singer. The result was that Gackt not only created and released covers of the winning songs, "Episode.0" and "Paranoid doll", but he also created a music video that was identical to the original "Episode.0" video, replacing art of Gakupo with himself dressed as Gakupo. Here is the original video , and here's Gackt's cover of it.
Development Hell: S.K.I.N played one concert and then... nothing.
Meaningful Name: Gackt's name tends to sound weird to, well... people in general. But his name has an actual meaning. Gackt Camui is a modification of Kamui Gakuto which can either mean "Divine power of music" or "Divine being made of music".
Ill Boy: He was hospitalized with a gastrointestinal condition when he was ten.
Mr. Fanservice: Gackt's appearance in Fuurin Kazan was expected to increase young adult female viewers. What they didn't anticipate was that he also drew in 40+ female fans as well.
One of Us: Gackt's fanboying is legendary. He has memorized all of the dialogue of the first Gundam series. His hairstyle for the Vanilla music video is based off of Super Saiyan Goku. The song Asrun Dream is about the characters Ash and Eiji from Banana Fish. He even once spent three days straight playing video games.
The Band Minus the Face: Malice Mizer. Averted when Tetsu left and Gackt joined they reached the height of their popularity. Played straight when Gackt left and later Kami died, as even after replacing Gackt with Klaha the band eventually broke up.
Training from Hell: Back stage footage of Gackt and his band preparing for concert is nothing but this. Gackt and his back up dancers "training" includes lifting each other as weights and taking turns punching and kicking each other in the stomach over extended periods of time.
Samurai: After his appearance in Fuurin Kazan Gackt started getting cast in roles as samurai. Since then he has been cast as Yoshi, a samurai in the film noir movie Bunraku, Nemuri Kyoshiro in a theater play, and even as Oda Nobunaga in Sengoku Basara: Moonlight Party.
Colbert Bump - Part of the reason he keeps appearing in so many video games and dramas. His appearances in such often results in jumps in ratings, viewer ship, and sales.
Crowning Music of Awesome - Pretty much all of Mars, Rebirth and Crescent, especially "Birdcage, Oasis and Oreinji no Tayoui". Single-only songs include mentions also go to "Cube", "Blue" and "Uncertain Memory".
Although NEVER to replace Ai Wo Torimodose as Fist Of The North Star's iconic song, the song for New is widely recognized by fans as the best song the series' had since.
Memetic Mutation - A dark version of this. Gackt's decade old joke about being a 496 year old vampire has been quoted out of context for so long that even presumably legitimate news sources have treated this as a serious belief of his. He has since corrected this at the Nemuri Kyoshiro press conference, where he released his actual age to the public so the joke would die.
Also, within the fandom, his love of Hyde, "fiyaa" and his unceasing use of the word dakishimete in nearly every song he has ever written are memes.
''"I need joh fiyaa fiyaa fiyaa to keep me wahm / I gah too fill za fiyaa / Tu keep me wahm, I gah to feel it...fiyaaaaaa!!"
Memetic Sex God - He's been voted Japan's sexiest man, best looking in a suit, best looking in a kimono, best looking in a tuxedo and best looking as a samurai.
The song "Sayonara" is sad by itself, but the live version for "Requiem et Reminiscence" is especially heartbreaking. And lets not forget that it seems like he has to stop halfway into Emu ~for my dear~ when singing live, makes sense since it's a tribute song for Kami.
"Kono Daremo Inai Heya de (in this empty room)". "Doooooshite...daremo inai kooono heya de...karada ga...furueru n darooo...oshiete." Na na na na na...
Which translates as "Why in this empty room, is my body shaking? Tell me..."
"Last Song " is quite saddening, especially because of the way Gackt sings it.
"Tsuki no Uta" is, too.
Other Tear Jerker songs by Gackt include "Hoshi no Suna " and the Gackt/Hyde duet "Orenji no Taiyou ". The last one can cause some people to cry for all nine minutes and ten seconds upon hearing it. It doesn't help that it was used in a Tear Jerker movie (Moon Child). Equally tear-inducing is the live version , with all the characters from the movie except one very important one.