Sometimes, a character from the Capitol who has a change of heart can be very interesting. They might start to see the cruelty of the system they are part of and try to help the tributes in some way. Their journey from being part of the oppressor class to becoming an ally of the tributes would make them stand out.
The Hunger Games First Quarter Quell fanfic often explores unique and darker aspects of the Hunger Games universe. It might focus on the special rules of this particular quell, like having double the number of tributes. Many fanfics in this category try to expand on the characters' backstories and their relationships in the face of this more intense and cruel version of the Games.
One interesting concept could be the unique twists on the original Hunger Games premise. Maybe new types of arenas or challenges that are more extreme. For example, an arena that changes not just physically but also temporally, like having different time periods within it.
There could be a young girl from District 11 named Mae. She has a talent for climbing trees quickly, which she learned from her father who worked in the orchards. She's quiet but determined, and her climbing skills could give her an advantage in the arena.
A mute tribute who uses sign language to communicate. This character would add an interesting dynamic as other tributes would have to learn to communicate with them in a different way. Their lack of voice could be seen as a weakness at first, but they could turn it into a strength, for example, by being able to move quietly and surprise their opponents.
There are fanfictions that focus on the backstories of the tributes in the Quarter Quell. For example, a story that delves deep into the life of a particular tribute in District 12, how they grew up, what led them to be chosen for the Games, and how they feel about the Quarter Quell being different from the regular Hunger Games.
The rules. In the First Quarter Quell, the rules are different from the regular Hunger Games, and this is often a big focus in the fanfic. It makes the story more complex and challenging for the characters.
You can start by looking on popular fanfiction websites like Archive of Our Own or FanFiction.net. Use the search function and type in 'Hunger Games Quarter Quell' to get a list of relevant stories.
Katniss Everdeen is surely one of the most memorable. She's the protagonist, a strong and resourceful girl from District 12. Peeta Mellark is also very memorable. His kindness and his relationship with Katniss make him stand out. And then there's Haymitch Abernathy. He's a former victor who becomes Katniss and Peeta's mentor and his drunken yet wise personality is quite striking.
Well, Katniss is at the top of the list. She represents hope for the districts and her skills in archery and survival make her a very engaging character. Cinna, the stylist, is also quite memorable. He creates amazing looks for Katniss and is really on her side. And Effie Trinket, with her Capitol - like behavior at the start but then her gradual change, is a character that stays in the reader's mind.
For me, Finnick Odair is really memorable. His charm, his skills in the arena, and his tragic backstory make him a complex and interesting character. Johanna Mason is also a character you can't forget. She's tough and has her own way of dealing with the horrors of the Hunger Games. And of course, Primrose Everdeen, Katniss's sister, whose innocence and the love Katniss has for her drive much of the story.