Falling Stars by Rokas is a BattleTech/My Little Pony: Friendship Is Magic crossover. (Not to be confused with the Fallout 3/Lucky Star crossover)
A misjump brings two very different mercenary companies to Equestria: James McKenna VII's Dark Horse Brigade and Garth O'Connell's Desperadoes. When the latter takes a piratical interest in the planet, the former finds itself at a crossroads.
Compare and contrast The Thessalonica Legacy.
Tropes used in Falling Stars include:
- Carnivore Confusion: Rainbow Dash finds bacon wonderful, disturbing the others. The humans spend some time telling Equestrians that animals in their world are not sapient like them.
- Death of a Thousand Cuts: Pegasus-dropped rocks cannot One-Hit Kill a 'Mech, but in sufficient numbers they can do real damage.
- Did You Just Punch Out Cthulhu?: The Desperadoes 'Mechs severely wounding Celestia.
- Fake Defector: Seabreeze.
- Hand Cannon: Ivan's 18mm pistol.
- Hollywood Tactics: Justified. O'Connell is at heart a thug and terrorist and not able to properly fight an equal foe.
- Les Collaborateurs: Various ponies throw their lot in with O'Connell, including Trixie.
- Moral Myopia: A Desperadoes pilot gets his jimmies rustled when Rainbow Dash blows up his wingman, not caring about the casualties they have inflicted on the ponies.
- Mother Russia Makes You Strong: Ivan, who can carry and use a massive Gatling Good meant for Powered Armor and wrestles a manticore. And TAMES it. In midair.
- Outside Context Villain: The BattleTech side.
- Redemption Demotion: Luna can't use some of Nightmare Moon's powers like turning into an immaterial wisp.
- Shout-Out: James says the original Chew Bubblegum line before going to town.
- Luna uses a Shoryuken.
- Ivan introduces the Ponies to his Bearhunter Autocannon named Sasha
- Taught By Experience: Rainbow Dash has learned to fight manticores.