Caped Mecha

Humongous Mecha are inherently cool. Surely there's no way to make them cooler, right? Well actually, the mere addition of a Badass Cape can indeed make the coolest thing on Earth even cooler.

On a human, a cape is commonly worn simply to look good; this is particularly true if one is Royalty. Superheroes often wear them to take advantage of the Dramatic Wind and simply appear visually impressive (though some turn them to more practical effects). And, of course, a cape can be useful to wrap around oneself if the weather turns suddenly cold or wet.

On a robot, however, these factors are far and away cancelled out by the simple fact that, implausible though mecha already are, a cape would simply get in the way and not be very practical at all. But when you look this awesome, who cares?

Anime and Manga

 * The final battle of the second arc of Tengen Toppa Gurren Lagann features the Dai-Gurren sporting a scaled-up version of Kamina's red Gurren-Dan cloak.
 * In Lagann-hen,
 * Great General of Darkness from Mazinger Z and Great Mazinger wore a flowing, red-and-indigo cloak reinforced his badass image.
 * The Nine Great Demon Generals in Transformers Zone. Transformers only sometimes have these in general; either because they're hard to animate, or because they'd typically get torn up in transformation.
 * And the Demon Generals are, for the most part, giant or combined Decepticons from previous series. You really wouldn't think Predaking could make the caped look work, but it's not so bad on him, really...
 * The Gloucesters used by Cornelia and her royal guard in Code Geass. The Galahad from the second season was designed with a cape, but this never appeared in the animation.
 * Gundam, surprisingly, has quite a few.
 * The Rose Gundam in G Gundam had a (segmented metal) cape draping over its shoulders at some points. However, G Gundam is quite well known for its impractical designs.
 * Sandrock and the Maganac Corps in Gundam Wing often wear cloaks. This does arguably have a justification, as it could be used to protect the machine's joints from blowing sand as well as adding a small amout of camoflage. Officially, it's also an ABC Mantle (see below).
 * After the Time Skip in Gundam 00, Exia conceals its missing arm using a sort of half-poncho.
 * Crossbone Gundam: The majority of weapons used at this point in the Universal Century timeline are beam weaponry, against which the best defense is a beam shield - and while this is effective, most of the fighting is in space, where a bright beam shield is highly visible. However, the cloaks used by the Crossbone Vanguard (and the X series Gundams in particular) are ABC Mantles that act as ablative armor vs. beam weapons - and on top of that, they're black, which gives some degree of stealth and/or distraction in space.
 * Delta Astray's Gundam Astray Out Frame has the Shooting Cloak, which covers its whole body and acts as active camouflage; however, since Out Frame is geared towards photography and journalism, the main function of the cloak is to keep Out Frame out of battles.
 * A few MS have metal parts (often taking the form of wings) that can wrap around the body like an armored cloak. This list includes Master Gundam, Deathscythe Hell (both versions), Astray Blue Frame Fourth, and Dynames.
 * Escaflowne, Scherazade, and pretty much every other customized or named Guymelef in Vision of Escaflowne.
 * The bad guys had capes that functioned as cloaks of invisibility as well.
 * It does make some sense on the Escaflowne since it represents the wings while in dragon form.
 * Getter Robo - specifically, Getter 1 uses it to fly.
 * In the Armageddon OVA, the cape is used in a whip-like fashion to wrap around a Mass Produced Getter Dragon's head before Ryoma punches it clean off.
 * In Neon Genesis Evangelion, when Asuka is introduced, her EVA is covered by a tarp. She wraps the tarp around her robot for a cape-like effect when she makes her battle debut. And it is awesome.
 * In Basquash, Dan's Dan Gan Go is sporting a cape when it first apppears at the BFB game in episode 1.
 * Billy in Xenogears had a cape for his gear. It looked odd on PS 1 graphics, when everything else was kind of blocky.
 * Ramrod from Saber Rider and The Star Sheriffs. It even has a Nice Hat.
 * Found amongst the Humongous Mecha mooks summoned by Precia to protect her Ominous Floating Castle at the end of Magical Girl Lyrical Nanoha's first season. She was going for a knight theme from the looks of them.
 * Volume four of the Appleseed manga takes this to the logical conclusion. At one point, several police Landmates show up wearing clothes: A jumpsuit with gloves. The Appleseed Databook specifically states that this is to protect them from dust.
 * When Dan crashes the Bigfoot Basketball game in the first episode of Basquash!, his Bigfoot mecha is wearing a tarp as a makeshift, but still cool, cape.
 * Gun Buster has the Buster Shield, which also works as a shield. (Seeing a pattern?)
 * It's sequel, Diebuster, has the semi-autonomous mecha Dix-Neuf wearing a cape duster jacket which is apparently rigid unless the pilot is in control. It also serves as a covering when the mecha is in rocket mode.
 * In Shinkon Gattai Godannar, Ken's Blade Gainer wears a cape, or rather what's left of it to emphasize his mysterious Badass attitude. And maybe to protect against sand.
 * When Scavenger first shows up in Transformers Armada he wears a large, body-covering cloak in the manner that a human might wear one to hide his identity. It actually looks pretty silly.
 * And Megatron's dream world shows him wearing a sash fastened with a Decepticon-sigal brooch.
 * In the manga Break Blade, a group of mecha in the desert is seen briefly wearing cloaks. They're not really capes, and are probably actually more for camouflage than to look cool, but they're still giant robots wearing huge pieces of cloth over their shoulders.
 * Borcuse's golem along with the golems in his retinue all have full size cloaks, in order to conceal all the various extra weapons added to the golems frames.Delphine has one with the same function.
 * Metal Robotnik in the Sonic the Hedgehog OVA.
 * While technically not mecha, many Mega-level Digimon, most famously several Royal Knights, are mecha like in size and appearance. Obviously, they wear enormous capes. Probably the most recognizable is Omnimon, whose size can be seen in this clip (for those of you who are impatient, skip to 2:04).
 * Gigantic Formula has the Jupiter-II (no, not that one).
 * Gun X Sword has Bolkain, who has a shredded wraith-like cape that can neutralise laser weapons and absorb them.
 * Gun X Sword has Bolkain, who has a shredded wraith-like cape that can neutralise laser weapons and absorb them.

Fan Fiction

 * In Undocumented Features, Corwin Ravenhair pilots a heavily modified Zaku in a G Gundam exhibition fight. This Zaku has a flex-metal cape that produces an Anti Gravity field, allowing its maneuvering thrusters to let it fly even on Earth.
 * In An Entry With a Bang!, when the battle of Port Krin seems to be going quite wrong, Tony Dansel has his team equip their Mechs with improvised capes.

Film

 * Transformers the Movie put Starscream in one for his coronation... and a crown, too. They've since become an iconic part of the character's look, and it's possible to get them as aftermarket accessories for the action figure, as well as PVC figures and statuettes of Coronation Starscream.
 * From what we've seen of from Dark Of The Moon, his back kibble is designed to look like a cape.
 * And  new design for the film has him wearing a cloak.
 * Los Dark's Fake Gokai-Oh from the Kaizoku Sentai Gokaiger movie.

Tabletop Games

 * At least one Tau commander has decided to mount a loincloth on his battlesuit.
 * A mech commander in Dragonmech commissions a velvet cape for his 120 foot tall mech. It gets lit on fire two weeks later, with predictable results.

Toys

 * Vezon from Bionicle wears a black cape, possibly to hide his lack of a spine.

Video Games

 * Aussenseiter in Super Robot Wars - justified in that it uses the cape to hinder the enemy sight as it blasts the enemy.
 * Which doesn't explain why it has a brand new cape every time it uses that attack...cape dispenser?
 * Also, the Vaisaga, which can also deflect enemy fire with it.
 * SRWJ's Granteed grows one out of pure energy with certain attacks.
 * The Ardjet in Zone of the Enders: the 2nd Runner has a functional cape which can rearrange into a coffin or separate into an Attack Drone swarm.

Western Animation

 * Not exactly a cape per se, but Lockdown from Transformers Animated brifly wears a rather fashionable poncho for a few seconds in one episode, before throwing it aside to attack Prowl. Given that the episode was called A Fistful Of Energon, this was probably a Shout Out. Red Alert of the same series, however, has her 'clothing' thicker, made of metal, and apparently forming a decent portion of her vehicle mode.
 * Most "Shellformers" have this feature. Fans tend to be divided on it because it indicates laziness on the designers' part.
 * Alpha Trion of Animated also bears a cape, though a quick glance at his design doesn't seem to support any sort of transformation, possibly a Shout Out to G1.
 * Alpha Trion, Optimus Prime's "father" in Transformers Generation 1, wears a cape, but he doesn't have to worry about it getting caught up in the works when he transforms because he's so old that he doesn't turn into anything: he was created before Cybertronians could transform. At least, the original series' version was. In how this relates to other series that have him but make transformation something all Cybertronians have always had is unknown.

Web Comics

 * In The Inexplicable Adventures of Bob, Roofus takes to wearing a large sash after he becomes a member of Princess Voluptua's royal court.