Skyscraper Messages

Skyscrapers are very tall and covered in windows. This makes them a useful canvas for a creative person to turn into a message an entire city (or the world) can see.

Skyscraper Messages come from lighting specifically chosen windows in otherwise dark buildings to make recognizable images or words. The trope, of course, only occurs at night.

A poor man's version of Rushmore Refacement or Deface of the Moon if a villain is behind it.

This trope is easily doable in Real Life, but limited to special occasions because it's otherwise disruptive to the people in the offices and apartments. In the movies, the trope is often assisted by computer animation; it's easier than getting the permits/paying the money to use the building, etc.

Anime & Manga

 * In City Hunter at one point, the lights formed the katakana version of the woman's name and "daisuki" (I like you a lot/love you.)
 * On Case Closed, the Suspect Of the Week uses such a window lighting event to give himself an alibi to murder his victim.
 * And in Magic Kaito, Kaitou arranged for a pair of skyscrapers to display a birthday message to Aoko once.

Comic Books

 * A 1970s Spider-Man story has the Shocker doing this with whole city blocks as part of an extortion scheme. Unsurprisingly, a later story has Electro doing the same thing.
 * The cover of one (UK version) Dennis The Menace album has Dennis and Gnasher being chased out of a building after doing this.

Commercials

 * One Chik-Fil-A ad has cows wandering through an office building, turning lights on and off (while late-working folk look up in wary confusion). At the end, the lights spell "Eat Mor Chikin" on the side of the building.

Film

 * In Hackers, the finale has Crash having rigged windows visible from their Rooftop Swimming Pool to read "Crash + Burn", which really impresses Burn that much more.
 * The finale of Sleepless in Seattle puts a giant red heart shape on the four sides of the Empire State Building.
 * Fight Club

Live Action TV

 * An episode of CSI had a business do this to try and win back his former fiance..
 * In Furuhata Ninzaburou, such a window lighting event breaks the suspect's alibi--the hotel where he was staying was spelling out its name in lights, and if he was in the room with the drapes open, then it would have ruined the character.
 * One episode of Barney Miller has a call about a man on a ledge. It's quickly followed by a report that the man is writing on the windows. Barney asks "It's not a jumper?" Wojo replies "Unless it's a suicide note."

Music

 * The music video for Black Eyed Peas's "Where Is The Love?" has lights spell out a question mark.

Video Games

 * A hotel in Grand Theft Auto Vice City will, in typical Rockstar North fashion, light up at night in the form of an erect penis. In Grand Theft Auto Vice City Stories, the same hotel shows the same thing, ejaculating.

Web Original

 * The original "All Your Base Are Belong to Us" video had one.

Western Animation

 * Batman the Brave And The Bold during "The Music Meister Sings The Song The World Wants To Hear", two skyscrapers behind him spell out the name of the villain.
 * In the episode of Danny Phantom where Danny is dating Valerie, the two of them see building lights writing out "D+V" while riding a Ferris wheel. This was all set up by Technus as part of a plan.
 * The Critic did a parody of the Sleepless In Seattle thing, with Siskel And Ebert. They Lampshaded it.

Real Life

 * Actually done at MIT with the Green Building. They've played Tetris by altering its lights.
 * Brown sees your Green Building, MIT, and raises you "La Bastille" (the aforementioned Tetris on the side of a building).
 * Many office buildings light up windows to shape stars or Christmas trees during the holidays.
 * Done for real in the city of Chicago for various events; most recently, as a countdown for the Olympic committee selecting who would be hosting the Summer Olympics in 2016. Regrettably, Chicago did not win.
 * Taipei 101 does this for most holidays. e.g. A heart for Valentine's day, E=MC2 for Einstein's birthday...
 * An archive of some of the ones Chicago has done over the years is here.
 * P.I.W.O. Light Show.