There is some well done fan made RKS content that I think deserves to be here on the fan works section. If I don't get around to it, can someone else consider adding it?
https://www.youtube.com/watch?v=l-wovgMsRJs
Mario - the fourth sector
A hack of a mario game with Spiritia as a playable character, alongside Mario and Sonic. Includes boss fights against Iris and Eifer, as well as many more RKS references in the dialog.
https://www.youtube.com/watch?v=gBXX2eFYjn4
Ike Man
A youtube animation in multiple parts that is made to look like a game despite not being one. The main characters are Spiritia and Ike from Fire Emblem: Path of Radiance. Despite being named after Ike, both he and Tia get equal "play" time. Grolla also makes a major appearance, and there are a few minor references to other RKS characters, like Freudia and Sichte. Warning, contains some off color content.
https://www.youtube.com/watch?v=2oJjefFUgoA
A youtube animation that is over an hour long and is an alternate retelling of RKS. It is darker than the game actually is and has a lot more death. I don't care for it due to this, but I am still mentioning it since it clearly took lots of effort.
There is also an I wanna be the Guy clone out there with Raimund Seyfarth in it, but when I downloaded it I couldn't get it to work and it gave me a Game Maker error. The game apparently also has Sonic in it.
http://kayin.moe/iwbtg/forums/index.php?topic=16176.0
Also, this is my own latest project, which currently has Spiritia, Freudia, Grolla, and Zorne all playable in it. I might consider adding something about it in the future.
http://biancagames.com/rokko.htm
https://www.youtube.com/watch?v=3A_YbZOQebc
https://www.youtube.com/watch?v=b__3gx8wApE
https://www.youtube.com/watch?v=wvD0QCw7Lls