Implausible Boarding Skills

Conventionally there's surfing, skateboarding, snowboarding, and sandboarding. Fiction expands the boarding to all sorts of media, and even with improvised boards.

See also Cool Board and Shield Surf. Sky Surfing is much cooler than what it is in real life.

Advertising

 * The TV commercial for the Shaun White Skateboarding video game has Shaun White boarding down a skyscraper.

Anime and Manga

 * Eureka Seven: the series is ALL about surfing, with the protagonists surf on Trapar, a mysterious energy spread in the air that comes and goes as it pleases. With enough trapar in the air, you can even surf inside your Humongous Mecha.
 * Pokémon Special has the finale of the Yellow Arc, where Yellow lavasurfs during the final battle and creates a massive whirlpool of lava that engulfs Lance.
 * Code Geass has a Crowning Moment of Awesome from the second season where Lelouch causes the plates that make up Tokyo to collapse, then uses a police mecha's riot shield to surf to safety. Among his feats, we get him grinding on the wires of another mecha's Grappling Hook Pistols, decapitating it as he jumps off.

Comic Books

 * There's a bit in the Star Wars Expanded Universe where one of Luke's childhood friends, Fixer, is tired of Luke and Biggs beating him at racing and the various other sports, so he invents sandsurfing. Trouble is, the moment they pick up on the sport, Luke and Biggs start to surpass him, so he ramps it up. Eventually he tries to jump over the Sarlaac pit. And fails, meaning that his two friends have to save him from a truly horrible fate. After that, they agree that Fixer's the king of sandsurfing, but somehow it doesn't feel as good as he thought it would.

Film - Animation

 * Disney's Tarzan slides through moss-covered branches in a manner not unlike surfing. This "surfing" was a typical "Disneyfication" by the animator in imitation of his kid skateboarding.
 * Robots: Bigweld surfs on a giant domino over a cascade of falling dominoes.
 * Hoodwinked: Granny Puckett surfs down a sky bucket cable on a muffin pan.

Film - Live Action

 * Back to The Future
 * Marty makes a skateboard out of a soap-box derby car.
 * In Part II, he makes one out of a girly pink hover-scooter by breaking the handle bar off. It's ok though, the little girl he stole it from ends up with a way more badass actual hover-board that belonged to the villain, so she tells Marty he can keep the pink one.
 * Herbie is a car, but he surfs in the movie Herbie Rides Again and in Herbie Fully Loaded grinds on a guardrail after watching Maggie do some skateboarding tricks.
 * In the Mr. Magoo movie, there's a scene where a chase down a mountain combines with a ski event. The good guys and the bad are on skis and snowmobiles and--Mr. Magoo is on an ironing board? He rides it like a scooter and wins the competition.
 * In X Xx, Cage pulls off a boardslide on an enormous handrail using a stolen serving tray. He even manages to jump between handrails. And later he snowboards in front of an avalanche on a wave of CGI.

Toys

 * Bionicle: Lava Surfboarding, and it's even a sport, on the island of Mata Nui.
 * In BIONICLE: The Game and Mask of Light, Kopaka's Ice Shield is used as an improvised board.
 * Disk Surfing in Metru Nui, which Exactly What It Says On the Tin ... in chutes.

Video Games

 * Prototype: the Body-Surf attack. Kick over (or up) an enemy (i.e. any living being) and use your momentum to ride their body down the street (or through the air, or other people). You know, just in case you didn't have enough sadistic ways to kill people already.
 * Ultimate Marvel vs. Capcom 3: the opening movie has Deadpool surfing on Phoenix Wright's OBJECTION speech bubble trough an explosion.

Web Original

 * Whateley Universe: Riptide, who is an aquakinetic, has a deviser hoverboard that runs on her own wave power, so she appears to be surfing across the sky on a little cloud. Thrasher is a skater boy who has PK powers and so his skateboard is a PK construct that can slide across anything, and go uphill.