I just copy-pasted this list from my blog. Feel free to use any of them, just let me know beforehand, as I may end up writing some of these myself eventually. Also because I'd want to read them.

Code Name: STEAM Adaptation

Have you ever wanted to see Applejack kick a mini-Cthulu in the face? Then this action/comedy is for you. See, Code Name: STEAM is a recently released 3DS game where president Abraham Lincoln puts together a team of elite agents to defend a steampunk alternate reality from the hostile takeover of eldritch horrors. Said agents are all borrowed from famous works of literature, including the four main characters from the Wizard of Oz. Just swap Oz for Equestria and bam, instant pony fic. Applejack, Bon Bon (yay ep100), Daring Do, and Twilight would be included. Let's face it, Dash and Pinkie would suck at stealth missions, while Fluttershy and Rarity would just faint on the spot the minute they laid eyes on a single abomination.

Archer Crossover

As in the show on FX, not the stupid character from FSN. Here's the premise. You know how the latest season of the show ended with Archer announcing that he had a brilliant moneymaking venture? Well, it fails miserably, but Krieger has a better idea. See, he uses his hologram technology to bring the Mane Six into being, with the intention of making bronies pay out the wazoo for a chance to meet them. The only problem? The ponies are self-aware. And they want to go home. Antics ensue.

Beauty is in the eyes of the Beholder

Ingeniously punny title aside, not sure how unique this would be. It would somehow involve a D&D Beholder. You know, one of those floating heads with the one big eye and a bunch of smaller, laser-firing eyestalks. The elements could fight one. Or maybe it shows up to ask Rarity for a dress, I dunno.

Luna OP (And also an Idiot)

Upon rewatching 'For Whom the Sweetie Belle Toils', I realized that Luna could somehow project real events into ponies' minds, from those they hadn't witnessed to those that had yet to occur. So, if all of time is within her grasp, why the hell didn't she realize that the whole Nightmare Moon thing wasn't going to work? Because she's stupid, that's why (still best pony, though). After a bout of depression prompted by this realization, Luna takes it upon herself to mold the future to her liking. This involves a spell to turn everypony nocturnal and trade roles with her sister. Hue hue hue hue hue.

Selector Infected WIXOSS Adaptation

The best way to describe the WIXOSS anime would be as a blend of Yu-Gi-Oh and Madoka Magica. So, girls playing a crazy card game to get their wishes granted, until it gets really dark. I'd argue the show is a hidden gem in the states, packed with emotion and intrigue. Its themes of friendship, determination, and hope mesh nicely with the world of ponies. Unlike the others, this fic would be on the long side, eventually having a chapter for all 24 episodes. An alternate universe would be employed here, as I'd have to alter the ages and relationships of many characters, as well as change the setting to Manehattan. Applebloom would most likely be the protagonist, with Rainbow Dash, Fluttershy, Trixie, and Twilight playing other key parts along with some other show ponies and OCs. If this sounds super interesting, don't go watch the show until I figure out if I'm tackling this, spoilers will ruin the drama.

OvereYAKting

So, Party Pooped just happened. The yaks were great. Now there should be a fic detailing some of the daily lives of the yaks. Naturally, any minor problem would instantly devolve into an enormous brawl. And of course Yakyakistan would somehow still be better off than Griffinstone.