Thirty Second Blackout

A piece of Applied Phlebotinum goes awry. It could be an accident, or by design. In any case, the whole city, or possibly even the entire surrounding region, goes dark.

About 30 seconds later, the power comes back on and everything is back to normal. Of course, this isn't very realistic. As was evidenced by the Northeastern U.S. Blackout of 2003, when a blackout of that magnitude occurs it takes hours or days simply to restart all the systems, even if no elements of the power generation or distribution infrastructure were actually physically damaged. While brown-outs may be brief, they generally only affect a small area, and anything that actually disrupts power generation or transportation will take significantly longer. It takes several hours just to get three generating stations running, then there's synchronizing with other generating islands, and slowly switching in load being careful that you don't overload the generation you have and accidentally cause another system collapse. In real life, it can easily take more than a day to restart an electricity grid after the initial blackout.

Anime and Manga

 * Justified in one episode of Neon Genesis Evangelion. In order to defeat an Angel, all of Japan was deliberately blacked out so the electricity could power a mecha-sized beam rifle.
 * In a later episode, though, a blackout shuts down Tokyo-3 for around the length of the episode (probably an hour or so), and everything comes back up almost instantly afterwards.
 * Not everything. The blackout happened in midday, and it's shown that power in the city doesn't come back on until nighttime. While we do see power in the Geo-front come on before that, we never see how much time it takes, and it was possibly one of the "backup" generators.
 * In an episode of Mahou Sensei Negima, Evangeline saps the energy from the entire city's power-grid to power her transformation into an 'Adult Form', allowing her to use her vampiric and magical powers unhindered. It only lasts for 5 minutes or so, though, and the second it runs out, the entire city flicks back on.
 * In the manga, the blackout was already scheduled, it was something they did twice a year for maintenance purposes. It was originally scheduled to be four hours long, but at the climax of the battle, the power comes back on 7 minutes and 27 seconds earlier than scheduled.
 * Possibly justified in Code Geass by the Gefjun Disturber, a device that retards the natural superconductive properties of Sakuradite. As soon as the Disturber is deactivated, anything it was affecting starts right back up.

Film

 * An electromagnetic pulse weapon used by robbers in Ocean's Eleven. According to dialogue, though, this is all it was supposed to do. (Note: Real EMPs do not work like this.)
 * In the original, they blew up the power lines.
 * Lex Luthor's experiments in Superman Returns.
 * An alien power generator activated in The Last Mimzy.
 * This happens in the Men in Black II movie.
 * The film Deja Vu has one whenever anything is sent into the wormhole.
 * In the original The Day the Earth Stood Still, Klaatu has a small demonstration where he deliberately, briefly shuts down all power except hospitals and planes.
 * Parodied in Airplane!, where the lights go out for a half-minute because Johnny unplugged them.

Literature

 * The Stand goes into detail about the enormous undertaking it would be just to get the power running in Boulder. It takes weeks of work from dozens of people to get everything running again. Especially since they initially didn't account for all the appliances left running when people died of Captain Trips. The grid was promptly overloaded on the first try, causing everything to go down again.

Live Action Television

 * Crusade's Excalibur vessel has about a minute of blackout after using main guns at full power. See also Fate/stay night.
 * Stargate SG-1 had a similar subversion to Evangelion, but with 80% of the United States blacked out to power a cloaking device so that the Ori ship didn't destroy the SGC and take over Earth. In an alternate universe.
 * The difference from a normal blackout is that the President warned the population to prepare.
 * Possible example from the teaser of "Avenger 2.0" when Felger's experimental plasma weapon shorts out and knocks out the base's electricity. After the titles, power's back. However, we don't know how much time passed between the teaser and act one. It's also possible all the weapon did was trip the main breakers, but that would make it a case of Artistic License - Electrical Construction: only the breaker the weapon was attached to should have tripped.
 * Star Trek: The Next Generation suffers one of these aboard the Enterprise when the computer drains power to create Moriarty, a powerful computer-generated character, on the Holodeck.
 * In the Star Trek (original series) episode "Bread and Circuses," Scotty uses the Enterprise to disrupt the Roman capital's power grid for a few seconds. Naturally, the blackout happens just as Kirk's about to be executed on live television.
 * Scrubs had it, with Doctor Kelso encouraging everyone to stay calm because the emergency generator will kick in. Kelso is relieved when the lights come back on, because he had no idea if there was such a generator.
 * This is Justified Trope of course, since this is not "power coming back" but rather the delay before the emergency generators start. This can take anywhere from immediately to few minutes.
 * Considering the setting one would hope to god that there's a way to justify this trope.
 * Kinda. Well, Kelso not knowing was Kelso being Kelso, but emergency generators for the main power system can take some time to get going, but essential devices (i.e. life support, lights in surgical theaters, etc.) have independent backups (and "life-essential" systems are usually on their own generator)
 * NCIS averted it when  took, if IIRC, at least a day and a half to resolve, which caused a lot of problems, both serious and mundane, for the team.
 * In The Cape episode "Goggles & Hicks", the titular assassins use an EMP-like device to shut off the power to the entire city for several minutes, so that they could not be tracked by the Cape's ally Orwell. When the device is turned off, the power is miraculously restored. No consequences are mentioned.
 * In the Firefly episode "Out of Gas", Serenity suffers a brief power outage during Simon's birthday party. Shortly after the power comes back on,

Video Games

 * Final Fantasy VII has a moment like this when a giant Mako Cannon is fired; the entire Midgar is slowly blacked out as the power is sucked into the cannon. We don't really see whether or not the power comes back on right afterwards, but Midgar certainly isn't blacked out in any subsequent scenes.
 * In Grand Theft Auto: San Andreas, there's an optional sidequest composed of several sub-missions preparing for a big cassino heist, Ocean's Eleven style. One of these missions involves planting remote controlled sticky bombs on the generators of the dam that powers the game's Las Vegas analogue, so they can be detonated and blackout the whole city during the heist. When it happens, the power stays off for a few minutes requiring the player to venture back upstairs and blow the cassino's back-up generators. Despite this, the city has power about a minute later.

RPG

 * A staple of Paranoia games. It's a classic for a reason, folks. To elaborate: In the GM section of the rulebook

Theater

 * In the Heights averts this; not only does the power outage last for days, but it is a major part of the plot. They even have a song about it.

Webcomics

 * The infamous Rickroll blackout of Megatokyo knocked the power out just long enough for the main crew to leave mostly unharmed for the next few panels.