My Personal Tierlist

(This list is by no way law, and is obviously not accurate to your own thoughts.)
{I didn't include Sandbar because he obviously smokes weed, and thus Transends the ranking system entirely.}

Explanation:
Best Horse:
Thorax, obviously. I think it is no secret that I practically worship him. He is adorable, noble and cute. So cute. He is also the show's best canon twink.

S:
Ember is really fun as a character, and she really shines when placed with Thorax and Spike who complement her so well.
Spike, while in earlier seasons isn't all that good, has really become good in season 6 onwards. He rocketed to the top of my list during some of those episodes in particular.
Gallus is my favorite of the young six. He is just so sarcastic, funny and sympathetic. Love him.
Ocellis is fucking adorable, and she is a changeling. Bonus points.
Pharynx wasn't on the website I used, but her is here. He is amazing, and his relationship with Thorax is the best brotherly bond in the show.

A:
Chrysalis is the best villain in the series, bar none. (Discord doesn't count any more.)
Yona is pretty hard to get a bead on, but she does have some really good episodes in my mind.
Shining Armor and Cadance, while by themselves pretty flat in my opinion just complement each other so well, and them interacting are some of my favorite moments.
Discord is discord. No explanation needed.
Silverstream is autistic yes, but in a good way. Her freak-outs and constant excitement is great in my opinion.
Twilight is the character who has, in my mind had the best character development in the series, going from a bookworm with almost nothing else going for her in season one to a relaxed and often times adorable character in later seasons.

B:
Luna. The fact that she triggered a civil war amongst the fandom in the early days of the show, is a sign that she is pretty popular. She also has a lot more character than her sister.
Smoulder is also cute. Her and Ocellus is one of my favorite ships in the show, only passed out by Embrax. She is however one of the weakest of the young six in my mind.
Garble? More like Chadle am I right?
Applejack is fun. Despite the fact that people hate a lot of her episodes, I don't. She is great.
Fluttershy is the cutest of every single one of the elements.

C:
Tempest Shadow is in my mind not as cool as everyone things she is. I don't really see anything really cool about her. Pharynx does the tough warrior act better. He is also better in general.
Vinyl Scratch. Her canon name is dumb, and she is on;y this high because she was in one of my favorite songs in the series (Love is in bloom)
Prince Rutherford is pretty characterless, but Yaks are best (But not best enough to get him too high.)
Novo is a sassy bitch. I love it, but she ain't sassy enough to be cool.
Pinkie is fun, but she is too random for me. Random comedy is honestly not all that funny to me. Reminds me too much of tumblr.
Rainbow Dash has a nice character, but like... half of all the problems in her episodes are her fault.

D:
Spa Ponies: No idea why they are here.
Sombra is what happens if you take Sauron, remove all cool parts of his character, and give him a gay as fuck voice.
Autumn whatever, along with kirins, are overrated. Autumn is just worse pinkie, and I cannot find what people like about the kirins. At all.
Rarity is the weakest of the elements. She also has abandoned her friends on like... 20 different occasions, used Spike as a pin cushion and is generally not all that good. I don't like her.

F:
Celestia didn't get an actual character until season 7. Until then she was literally just there.
Tirek is the most flat villain in the series. Especially now that Sombra has actual character traits now. (Like previously mentioned gay as fuck voice). Season 9 has been fixing that though.

Bottom tier:
The Storm King. All of this characters threats and traits only come from Tempest Shadow. Without her, he is literally nothing but a bland, forgettable villain with no real traits.