Добавил: The DSystem
Update: I have created a MUCH better skin with much more time put into it, it follows a similar rainbow theme, but looks a lot better. If you are interested in checking it out Click Here
This is my first ever skin EVER, so it was mostly just a test. I will be making more elaborate things in the future. If I did anything wrong please do not hesitate to tell me.
Extract the "Rainbow Heart Knife Skin" folder to Steam\steamapps\common\Team Fortress 2\tf\custom\
It should install automatically the next time you open the game.