One great 'Supernatural' fanfiction where Sam is injured is 'Broken Wings'. It delves deep into Sam's struggle to recover after a major injury, and how Dean copes with it. The author does a wonderful job of portraying the emotional turmoil of the characters. It also has some really interesting side plots involving the supernatural elements that we love from the show.
One common theme is the brotherly bond. When Sam is injured, it often showcases how Dean steps up to protect and care for him. Another theme is the struggle against the supernatural while being weakened. Sam may be injured, but he still has to face the threats out there. And there's also the theme of self - discovery. Sam might question his abilities and his place in the hunting world while he's recovering.
It's also possible that he gets injured while trying to save someone. Sam is known for his selfless nature. He could be rushing to protect an innocent bystander from a supernatural creature, like a werewolf or a vampire, and in the process, get bitten or scratched, which would lead to an injury.
Well, it depends on the plot. Maybe his brother Dean will go on a revenge spree against whatever injured Sam. He could start hunting down the creature or person with a vengeance.
In fanfiction, if Sam was kidnapped, it could lead to a very intense story. Dean would surely go on a rampage to find him. Maybe Sam was kidnapped by a powerful demon who wants to use him for some dark ritual. It could also be a new, unknown enemy who has a vendetta against the Winchesters.
Dean is almost always going to be in these fanfictions when Sam is gagged. Their relationship is central to Supernatural. Rowena could also be a character. She might use her magic to either gag Sam for her own purposes or to help him if she has a change of heart. And Gabriel. He could turn up and use his trickster abilities to either put Sam in the gagged situation as a joke or to get him out of a more serious one.
One great fanfiction is 'Sam and Rowena's Unlikely Alliance'. In this story, they team up to face a powerful new threat that the Winchesters alone can't handle. It has a lot of great character development for both Sam and Rowena, showing their complex relationship in a new light. The author does a wonderful job of capturing their voices, making it feel like an extension of the show.
One great fanfiction could be where Dean and Sam have to face a unique Halloween - themed monster. Maybe a witch who uses Halloween traditions to cast powerful spells. They would have to use their wits and hunting skills to stop her before she causes chaos in a small town.
There's this fanfiction called 'Sam and Jack: Unlikely Allies'. It starts with them being at odds with each other, but as the story progresses, they start to understand and respect one another more. The plot is well - paced, and the author does a great job of writing their dialogue in a way that feels natural to their characters.
One great Supernatural Sam Whump fanfiction is 'The Road to Recovery'. It focuses on Sam's struggle after a major battle. The author does an amazing job of depicting Sam's physical and mental pain, making it a very engaging read.