TWIPIE: So this is the best ship because they compliment each other so well. Pinkie can push Twilight to do new things and get away from her books while Twilight can bring Pinkie down to earth. They bounce off each other so naturally I think their relationship would be a ton of fun. I think this ship peaked in seasons 1 + 2 since they got so much screen time together. They got two co-star episode with Feeling Pinkie Keen and MMMystery, another episode where they were together for a good chunk of it with It's About Time, Twilight cameoed in both Pinkie's focus episodes in season 2, and they got a little moment in Luna Eclipsed. The ship was never the same after Twilight became a princess, but I can still revel in the golden days of TwiPie and I still think it's the best ship.

RARIPIE: There wasn't that much evidence for this ship until season 6, but I still can't help but think these two would work really well together. They both came from humble beginnings to follow their dreams. They can both be pretty extreme, but they can be there for each other when they go too far. They're both extremely creative and can create a very natural and breezy dynamic. I still prefer TwiPie because TwiPie is a lot more fun, but RariPie feels like the most stable ship for Pinkie and I kinda like it more the more I think about it. The best examples of RariPie are No Recipe For Perfection and The Combinatorics Project. Also read The Road to Ponyville. It's not romance, but it's a much better "road to" story than Road to Friendship.

RARILIGHT: Blame Monochromatic. There's really not much else I can say. She writes this ship so well that all I have to do to convince you of this ship is to tell you to read one of Monochromatic's stories. Maybe one of her shorter and fluffier stories.

RARIJACK: Ah. My old OTP. It's not that I don't love RariJack anymore. It's just that I like other ships more. Either way, this is still a really good ship. They're both hard workers who can respect each other and appreciate each other's quirks. The only reason RariJack lowered over the years is because I think it's not quite as interesting as the ships I put higher. Still, good ship. 

APPLEDASH: This ship is so obvious that it's kinda sorta maybe canon in the finale. And that's part of why the ship isn't any higher for me. It doesn't have the spark that my favorite ships have. But points for believability.

FLUTTERPIE: For a while I thought this ship could never work. I mean, they're pretty much polar opposites. But then I read Leafdoggy's series of FlutterPie stories and now I get it. If we’re talking about early Fluttershy and Pinkie, then this obviously wouldn’t work. Not all opposites attract. But if we’re talking about late series Fluttershy, this could totally work. As the show went on, Fluttershy developed more of a backbone and could easily call out Pinkie when she goes too far. Outside of that, I can see Fluttershy and Pinkie cuddling together and Pinkie helping Fluttershy with her animals. It’d be cute.

APPLESHY: This just seems like a cute ship. Nothing really stand out about it, but cute. 

TWISHY: Same as AppleShy. Cute, but not much more.

RAINBOWPIE: While Rarity and Pinkie get better the more I think about them, the opposite happens with Pinkie and Dash. That’s not to say I don’t think it could work because it can. Rainbow and Pinkie already have a strong friendship and that could morph into love. But Rainbow is pushing for higher things in life and Pinkie will try to spend more time with Rainbow in really dumb ways. Just look at Wonderbolts Academy. Honestly I think they’re pretty close to the tier below this, but I’ve seen too many solid fics about them to do that.

RARIDASH: This is an extremely explosive ship. They’ve both got ambition and they both have big personalities, but whether that’s a good thing or not depends on the writer. I can see it easily going both ways. I can see this being really fun or a complete disaster. Both make for good stories, but many of those stories end in a bitter breakup.

TWIDASH: I know that these two are the most popular ship, but I think I have an inherent bias against this ship because of TwiPie being my OTP. To be fair to them, I think Rainbow works with alicorn Twilight better than Pinkie. There are many reasons for that. Twilight lost most of her edge after becoming an alicorn (and thus her ability to keep Pinkie in check), Twilight and Rainbow gained more things in common (flying), and the show just shifted its focus towards Twilight and Rainbow rather than Twilight and Pinkie. But I can’t see Rainbow with unicorn Twilight at all. They both like reading, but there’s nothing else there.

TWIJACK: I don’t see much here. They both respect each other and I guess a relationship could work, but eh. I don’t really get it.

FLUTTERDASH:  I know that they’re childhood friends and I guess they can complement each other, but I can’t see them moving past friendship. There’s nothing about them that screams romance to me.

RARISHY: I don’t see these two going past friendship. A relationship could easily work, but when I look at Rarity and Fluttershy, I only see friends.

APPLEPIE: I don’t get this at all. There’s a reason this is the least shipped couple out of the mane six. I’ve seen attempts at making this work, but I’ve never bought them outside of a few short one shots and maybe The Combinatorics Project.

OMNISHIP: There’s some cute fluff with the omniship, but there’s no chance in hell that this could work in anything more than a short fluffy one shot. Polyamorous couples of three can work, but all of the mane six together is insane.

SOME OTHER SHIPS THAT AREN'T MANE SIX + MANE SIX:

SPARITY: This ship and all the others that ship Spike with one of the mane six are insane. Spike is a kid. This is creepy. (goes under No).

STARTRIX: There’s a reason there are so many episodes with these two. They have a great dynamic. They’re similar enough to get along well and Starlight is there to be the voice of reason when Trixie goes too far. (goes under Pretty Great).

STARBURST: Sunburst just doesn’t have enough personality to him. There is an episode in season 8 with just them and that was pretty good, but I just don’t get the same spark as I do with Startrix. Still, it does work. (goes under Solid).

FLUTTERMAC: These two just don’t have much interaction. I guess this could work since they’re both quiet and I could see Fluttershy having a crush on Big Mac, but the reciprocation is where I don’t quite get it. Still, it’s not bad. (goes under …it can work, I guess).

FLUTTERCORD: I don’t like shipping Discord with anyone. He looks like a creepy old guy so any ships with him are inherently uncomfortable. Fluttershy and Discord have a nice dynamic, but anything more than friendship is creepy as hell. (goes under No).

CHEESEPIE: Boring, but it works. They’re pretty much the same character so of course they have enough similarities, and I guess a fic could make some differences between them, but I can't see a relationship between them being interesting. The only place I saw a spark between them was in their Friends Forever comic, but that’s it. (goes under ...it can work, I guess).

TWILESTIA: I know Twilight is an adult and technically an equal to Celestia since they're both princesses, but this is still creepy to me. (goes under No).

So what have we learned? I've learned that Pinkie is the most shippable of the mane six with 4/5 of her ships being at least solid, though Rarity comes at a close second. Rainbow is the least shippable of the mane six with only 2/5 of her ships being at least solid.