One common theme is self - discovery. Harry Cold often goes through a journey where he learns more about himself. Another theme is friendship, showing how his relationships with others shape his character.
Another theme could be survival. The cold can be a harsh element, so in these fanfics, Harry often has to fight to survive, whether it's against the cold itself or the threats that come with the cold environment, like dangerous ice creatures or dark forces lurking in the cold.
I've heard of 'Emotionless in Hogwarts'. It's a fanfic where not only Harry but also some of the other characters start to show signs of coldness and lack of emotion. It could be due to a new type of magic that has seeped into the school. The story focuses on how they deal with this new state of being and how they try to reverse it.
One possible fanfic could be about a Harry Potter who has lost all his emotions due to a dark magic spell. He goes through his days at Hogwarts just going through the motions, not feeling joy at Quidditch or friendship with Ron and Hermione. His coldness could lead to misunderstandings among his friends and teachers.
One popular 'Harry Cold fanfic' might be 'The Adventures of Harry Cold'. It often features unique plot twists that deviate from the original storylines. The characters in it are well - developed, making the reading experience quite engaging.
There's also 'Harry in the Cold Realm'. In this fanfic, Harry gets transported to a strange, cold realm. He has to team up with some unexpected allies to find his way back home. The descriptions of the cold realm are really vivid, and it's exciting to see Harry use his skills in a completely different environment.
Perhaps he is trying to hide his true self. He may have a side of him that he doesn't want others to discover, like some special abilities or a different origin. So, being cold to everyone helps him keep his secrets and avoid getting too close to people who might figure him out.
The author could show his coldness through his limited dialogue. For example, Harry might give short, curt responses to others. This would immediately signal his distance.
A detective - themed fanfic might work too. Harry could be a detective in a gritty, crime - ridden city. He's cold because he has seen so much of the seedy underbelly of society. His use of guns comes in handy when dealing with dangerous criminals. He might be on a case that forces him to face his own demons as well as the external threats.