The Secret Service: an elite military unit especially trained to protect the ponykind from every kind of threat under the protection of secret identities.

Agent Lyra Heartstrings of the Secret Service doesn't belive in humans, she just pretends to for her identity's sake. She lives a happy life being secretly a hero, until Anthropology fan Sweet Pea turns Lyra's entire world upside-down when he reveals a dark secret about herself. A secret she wished she never knew.

Tribute to Anthropology by JasonTheHuman.
ONE OF THE BEST STORIES EVER, THANK YOU FOR THAT JASON

Six months after her defeat in her town, Starlight Glimmer comes to Ponyville seeking for revenge against the Mane 6; this time not only taking their Cutie Marks but destroying them as well.
Humiliated and defeated the girls simply disappear leaving the Kingdom at the mercy of its enemies for ten years… until the arrival of the Undead Knights. A group of seven unspeakable cruel monsters who protect Equestria at the costs of countless massacres, painting Equestria with the blood of its enemies.

Equestria’s ultimate protectors, the shadow of Harmony.

WARNINGS:

This story ignores Season 5 finale
And as all my other works this is a translation, the original can be seen here at FanFiction.

Trixie is a happy mare, now that she is Princess Luna's commander of the Undercover Police she haves everything she ever wanted: money, power and even the legal right to insult Princess Sparkle every time she wants without consequences. But one day doing community service in an orphanage, one colt calls Trixie’s attention and steals her heart. A different boy and a great challenge before her but there’s nothing Trixie can’t handle, so as Pure Soul.

This story is set on the Spike Lord of Chaos timeline, but has nothing to do with the main story.

As all my stories this is a translation. You can find the original here

A MLP/Generator Rex Crossover.

After being defeated by Twilight a second time, Trixie decides its time to start over again; now as a feared bounty hunter she gains her fame as Great and Powerful back and for real.
Now she has money, fame and everything she ever wanted... except for a friend; or that's until she finds a young pony with extraordinary powers and no memories of his past. Trixie decides to help him unaware that they can become more than friends.

As the rest of my works this is only a translation; you can see the original in spanish here

A Hellsing Ultimate/ My Litle Pony Crossover; a remake of one of my failed stories but after a while I reposted it on my fanfiction account in spanish, and finally decided to translate it. Again I hope you like it and is you read Spanish you can see the original here

Vampires: horrid creatures who tormented the already extinguished human race; vanishing along with their preys thousands of years ago. Or do they? Fluttershy accidentally awoke the last of the vampires, bringing back to Equestria the past horrors. GORE

CHAPTERS 1 & 2 EDITED BY boombox89 THANK YOU FOR ALL YOUR HELP!!

Also author Ocelot the Devil posted his own version and you can find it in here on FanFiction. Ocelot, I hope you like this new version, is quite different than my original one so you can keep going with your version.

This story is a sequel to Spike: Lord of Disharmony and Chaos

Discord retired, yes, he retired from being the lord of chaos; and now Spike is his replacement.
With fresh new ideas and all the energy of youth, Spike is ready to make the life of the Mane 6 impossible; along with his loyal partners: the CMC

As all my other works, this is a translation. You can find the original in spanish here

Muriel the Great Witch had the ultimate power to destroy humanity: a powerful book filled with all the secrets of the devil.
But when the witch hunters Hansel and Gretel murdered her, she left the book behind ready to be found by the correct witch.

Meanwhile, in the other world, Sombra freed from his prison and wanders all over Equestria looking for the power to defeat the four Alicorn Princesses once and forever; it's when he feels the dark energy from Muriel's book. Using all his power he travles to the human world ready to put his hooves on the book.
Unfortunately, with Hansel and Gretel waiting... that wasn't the wisest idea.

SPOILER ALERT: this story contains several information about the movie Hansel and Gretel Witch Hunters. If you haven't seen it yet, you've being warned.

Mane-iac is dying, but before she goes, she have a final request for her childhood friend

WARINING: euthanasia, if you don't agree, don't read

A nightmare night special based on Spike: Discord thinks is time for his retirement, but he needs to name a replacement first. Spike knows very well the Mane 6, specially certain Alicorn Princess. Who’s best to make their lives impossible?

You can find the original in spanish HERE

Also a serialized sequel HERE

Celestia and Luna's lost parents, the Princesses never met them, not even heard a single word about them. What's the truth behind their imprisionment so long ago?
Why they were separated from their beloved childs? And why are all the enemies of Equestria so affraid?