Pyramid Power

In the distant past, many civilizations built pyramids as monuments. The most famous are those of Egypt, followed by the Mayan pyramids in Mexico. They have also been found in Sudan, Iran, and China. The reason for the pyramid shape is quite simple and practical - 80% of a pyramid's mass is in the lower half, meaning that it is the most practical shape to support a building of that height. It's the form of stone building most likely to still be standing in a recognizable shape when the archaeologists show up a thousand years late to the party.

However, due to a mixture of the distinctive geometrical shape and the immense labor required to build them, a lot of people have assumed there must be some special significance to the shape. Or that they were built by aliens. Predictably, this also shows up in fiction. During the 70s there was an actual fad about the pyramids serving as a focus of cosmic energies ('pyramid power') and that resting in houses or boxes shaped like them could grant many physical and mental benefits. And sharpen razor blades.

There is also the incorrect belief that the Egyptian Pyramids were built by slaves; in actuality they were built by native Egyptian peasants who had no work to do during the Nile's flood season; they may have been press-ganged into it, but it's just as likely that they were enticed with offers of food (grain, veggies, and beef) in exchange for their labor. It was still still quite a feat of engineering and patience, though.

Anime and Manga

 * The Millennium Puzzle in Yu-Gi-Oh! is in the shape of a pyramid.
 * When Death The Kid is introduced in Soul Eater he fights mummies in a pyramid..

Comic Books

 * Subverted in Alan Moore 's ~D.R. & Quinch~: Two alien timetravellers indeed visited Ancient Egypt but they still cannot understand why the locals believed that the aliens wanted them to build pointy buildings.
 * In the Mexican series Chanoc a story featured the concept of Pyramid Powers (in a satirical way.)
 * In The Cartoon History of the Universe, the chapter on Ancient Egypt briefly mentions Pyramid Power, with an alien saying "Why build a pyramid when you can sharpen a razor blade in five minutes on a wet rock?"

Fanfic

 * "Pharaoh Andrew", an episode of Script Fic Calvin and Hobbes The Series, has the gang going to the Pyramids of Giza for Calvin's school report. They end up having to fight off some mummies.

Film

 * Because giant alien death robots who turn into awesome cars wasn't enough, Transformers: Revenge of the Fallen had them building and destroying the pyramid at Giza, which houses a solar power collector.
 * Alien vs. Predator also mentions pyramids in Cambodia.
 * Played with in National Treasure. Upon finding a complicated, ancient structure under a city, one character wonders how it was built. The protagonist replies that it was built the same way the pyramids were, and his friend confuses his intention, and assumes that he means that the aliens built them.
 * Pyramids are Forgotten Superweapons in Stonehenge Apocalypse, which is some kind of alien device that is a Countdown till The End of the World as We Know It. ... for some reason.

Literature

 * Pat Flanagan's 1973 book Pyramid Power. It popularized the notion that the shape of a pyramid, in and of itself, has mystical properties -- from preserving food to sharpening razor blades.
 * This is also the title of a book by Eric Flint, the second in a series. It involves a five sided alien pyramid landing in Chicago.
 * In the Discworld novel Pyramids, the pyramids act as "time dams", preserving the Old Kingdom unchanging for thousands of years. They don't sharpen razor blades, though ... they take them back in time to before they were blunt.
 * The late bible scholar Zechariah Sitchin wrote in his book The Stairway To Heaven that the Giza pyramids were in fact constructed as Navigation facilities (like those used in airports/space centers), by Ancient Astronauts no less.
 * In The Cat Who Blew the Whistle, there is a character named Elizabeth Hart who is big on the idea of pyramid power. Unannounced, she and her boyfriend pop over to the protagonist's (Qwilleran's) place and set up a makeshift portable pyramid. After they leave, Qwilleran's intelligent Siamese cat, Koko, makes his way to the very center of the pyramid and there is a blackout across the entire town that doesn't stop until he exits the pyramid.

Live Action TV

 * Stargate SG-1, apart from having the real pyramids in Egypt turn out to be ancient landing pads for Goa'uld spacecraft, also had Goa'uld-built pyramids appearing on alien planets as Supervillain Lairs and the like. The Goa'uld were the ancient Egyptian gods, after all. Their Cool Starships are also basically giant flying pyramids with extra high-tech superstructures added (which explains how they fit onto their "landing pads").
 * The original Stargate film had an even straighter example.
 * The original Battlestar Galactica Classic had the heroes find the lost planet of Kobol. The ancient pyramids on that planet looked suspiciously like the ones in the Giza Plateau. They contained a wriiten account of the Lost 13th Tribe, and where they went.
 * Myth Busters did an episode exploring the notion that a pyramidal shape can preserve food and sharpen razor blades. In the end, no significant difference between items stored in a pyramid and items stored in some other shape could be detected, and Adam admonished his cohorts against testing woo-woo myths like this again.
 * Done in the Nineties revival of The Tomorrow People. The plot is that an immortal Egyptian pharoah is trying to recreate the circumstances required when the stars align to give him great power, which requires him to move a bunch of obelisks all over Europe (supposedly explaining why they were brought to London, Rome etc in the nineteenth century). The protagonists point out that this would mean he would have to have built a central focusing pyramid in the middle of them, in central London...they then look behind them and see the pyramidal top of the Canary Wharf Tower. Note this was years before it was used as the Torchwood Tower in Doctor Who.
 * One of The Sifl and Olly Show's fake "Rock Facts" claimed that the pyramids of Egypt were built by humans, but it was in anticipation of the prophecied arrival of...DavidBowie.

Music

 * The Alan Parsons Project poke fun at the concept with 1978's "Pyramania", with the cover of its parent album, Pyramid, showing a copy of the aforementioned book by Flanagan.
 * Hipgnosis, who designed the cover of Pyramid, also invoked this trope with their famous cover for Pink Floyd's The Dark Side of the Moon.
 * The Grateful Dead's performance at the Pyramids of Giza (also in 1978) was a byproduct of this trope, with a total lunar eclipse taking place at one point.

Tabletop Games

 * The Tremere clan from Vampire: The Masquerade is obsessed with this trope, incorporating pyramid symbiology into the design of their rigid organizational structure in hopes of attaining greater mystical power. It doesn't work out very well.
 * In the Illuminati card games, the Bavarian Illuminati's Eye-In-The-Pyramid logo is used as Sigil Spam in all of the card illustrations. fnord.
 * In Through the Ages, the Pyramids grant you one extra civil action per turn. Arbitrary, but probably no less arbitrary than the powers the Civilization games gave them.
 * In Rifts, Pyramid Power is a major feature of the Atlantis sourcebook. They're like Ley Line dams, basically, and they were/are used both by the ancient Atlanteans and the Splugorth for things like dimensional travel.

Western Animation

 * In Transformers Robots in Disguise, one of the O-Parts and the Orb of Sigma were both hidden in different pyramids.
 * In Phineas and Ferb, Doofenshmirtz thought that the pyramids of Egypt was built by aliens, when the Egyptians used music to command the aliens.
 * Futurama:
 * One episode has an inversion. When the cast lands on an ancient Egypt themed planet, it's revealed that the Egyptians traveled to space and built pyramids on alien planets.
 * "That Darn Katz!" plays it straight: it turns out that the pyramids were built as antennas to beam the earth's rotational energy to the planet Thuban 9 (which is the original homeworld of cats).
 * In the fourth season of X-Men: Evolution.

Video Games

 * In the Civilization series of games, the Pyramids are one of the World Wonders which you can build for a powerful effect on your civilization. In the first game they allowd a change to any government type in the game. This was very powerful, as you could change to the goverments available late in the game in the very beginning and have a great advantage over the computer civilizaions. This was changed in the second and third games so that Pyramids grant a free granary to every city, letting your civilization grow more quickly. In Civ 4, they unlocked advanced forms of government long before you could otherwise attain them. In Civ 5, they make your civilian units work harder.
 * In La-Mulana, the "male" pyramid in the Egyptian-themed Temple of the Sun has a hidden link to the inverted "female" pyramid in the Temple of Moonlight. Using any weapon in the "female" pyramid is punished with a Bolt of Divine Retribution.
 * The Temple of the Ancients of Final Fantasy VII did not produce or direct power, it was power--being a giant maze which when solved would shrink into its smaller form, the Black Materia that would summon Meteor and bring about the Endofthe World As We Know It.
 * In the game Serious Sam you tour ancient Egypt to find the reason Aliens took over the world in the distant future. After you collect the Sun Orb and arrive at the sun pyramid, and places the orb at its place, it appears that it actually some sort of a communication tool to communicate with aliens. Apparently you need their deadly lazer beam in order to destroy the normally immortal final boss.