I've written and read a couple stories that would fall into that category, so I am proposing the idea for a category being added on this website, so I can change my stories from "Other" to "Fairy Tail"
Characters who would be included:
Girls:
Lucy Heartfilia
Erza Scarlet
Juvia Lockser
Wendy Marvell
Carla
Levy McGarden
Mirajane Strauss
Lisanna Strauss
Cana Alberona
Evergreen
Ultear Milkovich
Meredy
Yukino Agria
Boys (In case they have some sort of involvement in the story)
Natsu Dragneel
Happy
Gray Fullbuster
Elfman Strauss
Gajeel Redfox
Panther Lily
Laxus Dreyar
Freed Justine
Bickslow
Jellal Fernandes
Sting Eucliffe
Rogue Cheney
There are many more, but those are some characters who I'd consider invovling