"I just run," said the unicorn, "Just run and run."
"That sounds boring," replied Twilight.

When a strange robotic unicorn appears in Equestria, hailing from a world of pixies and dolphins, Twilight and the rest of the Mane 6 must work out what to do.
Soon they discover a much darker side to this robot's tale.

A crossover between MLP: FiM and Robot Unicorn Attack, the manliest game ever!

Set in an alternate universe where ponies discovered technology and "put it to bad use" is an understatement, the small filly Sweetie Belle (who has a different personality in this universe) decides to make things right. With the help of **** ***** *** *******, she will face the Mane 6. Well, only some of them due to some of them ***** **** and one being *** **** ****.

WARNING! IF THIS FANFIC WAS A FILM, I WOULD BE A 12A!
CONTAINS SCENES OF VIOLENCE, DEATH AND CRUELTY.
DO NOT LET YOUNG CHILDREN READ THIS FANFIC!
OR IF YOU JUST PLAIN DON’T LIKE PONY VIOLENCE, DON’T READ IT EITHER!
YOU HAVE BEEN WARNED!

I have no idea whether this reflects what the story is like or not, but I gave it a tag of Teen.