One type of fanfiction could be where Sam gets hurt during a hunt. Maybe he's attacked by a powerful supernatural creature and has to deal with a serious injury while Dean tries to find a way to save him. It could explore his physical and mental pain, and how he copes with the situation.
Perhaps Sam gets hurt while trying to protect a civilian. He jumps in front of a werewolf's attack meant for someone else. This would show his selfless nature. The local hunters in the area might not trust Sam and Dean at first, but seeing Sam's sacrifice could change their minds, adding an interesting dynamic to the story.
I really liked 'Ruby's Redemption in Sam's Eyes'. In this fanfic, it takes a different turn where Ruby seems to be on a path of redemption through her connection with Sam. It shows a more vulnerable side of Ruby that we don't often see in the show. It's a great read if you like exploring the emotional side of their relationship. And there's also 'Sam and Ruby: The Hidden Bond' which uncovers a hidden, deeper bond between them that even they are not fully aware of at first.
Fanfiction about Sam and Lucifer in the 'Supernatural' universe can be quite interesting. When it comes to the 'lemon' part, it could be a way for writers to delve deeper into the relationship between these two characters. Maybe it's about Lucifer's attempt to corrupt Sam in a more intimate way, or Sam trying to use his own charm or connection to gain an upper hand over Lucifer. But it also might not be as straightforward as it seems, and could involve a lot of psychological twists and turns.
One common theme is the struggle for acceptance. Sam has to deal with his own self - acceptance of his pregnancy, and also get acceptance from his friends and family in the 'Supernatural' world.
The theme of self - discovery is also quite prevalent. As they go through various adventures, Sam and Jack learn more about themselves, their powers, and their place in the world. And family is another important theme. Even though they may not be related by blood, they become like family in many of these stories.
Another aspect is how it affects the relationships in the story. If Sam is hurt, it can put a strain on his relationship with Dean. Dean might feel guilty for not being able to protect him. Or it could strengthen their bond as Dean devotes all his time to taking care of Sam and making sure he gets better.
Loneliness can be a theme too. After being betrayed, Sam might isolate himself, feeling that he can't trust anyone anymore. This can lead to him making some rash decisions. And the theme of revenge also pops up sometimes. Sam may seek to get back at those who betrayed him, which can take the story in a whole new direction.
One common theme is the struggle between good and evil. Sam is often seen as a force for good, while Amara represents a more ambiguous power. Their interactions can be seen as a battle of wills in this regard. Another theme is redemption. Amara's character, being a powerful and somewhat 'fallen' entity, often has storylines about her possible redemption through her relationship with Sam.