If they were to turn certain characters gay who would be the likely candidates?

[Mysterycat 27]

Well, we know Twilight and Rarity have dated stallions, and are therefore not gay but could be bi. Same goes for Flash Sentry, who has dated a mare, and Carrot and Cup Cake, Shining Armour, the parents of the main characters, and Princess Cadence who are married to the opposite sex.

Cranky and Matilda can't be gay as they are love interests, and Flurry Heart, the Cake twins, Dinky, Diamond Tiara, Silver Spoon the CMC, Rumble, and Pipsqueak are all too young.

That leaves Luna, Celestia, Fluttershy, Big Mac, Applejack, Derpy, Pinkie Pie, Zecora, Lyra, Bonbon, Rainbow Dash, Granny Smith (although she has had foals), and Discord.