My favorites champ always have a weird motive why i like them.
Vi = She is the reason i started playing league of legends, her neon strike skin, is based on franky from one piece, and that is how i knew about the game, and since i started playing, i wanted to get the champ and the skin, but the more i played her, the more i liked the character, and i have all of her skins.
Soraka = Since playing world of warcraft, making my beautiful lady night elf (i never got far into WoW, boring game), i always found that this tone of blue/purple in a female skin very beautiful, and soraka is such a good character, and she was my first support. (and i know soraka looks more like a draenei, but is the tone of the skin that is important here, and draenei are beautiful too)
Annie = The first main, we never forget, she was my first main, and boy do i love to burst entire teams with tibbers.
Sona = Her pentakill skin is awesome. She is beautiful.
Leona = What a tank, is so fun to play with her as support.
Shen = A funny video made by some youtubers here in brazil made me like him, and is so fun to use his ult to save people.
Jax = He is badass.
Xin Zhao = Easy mode jungle in season 4. =P
Mundo = Another champ to have fun, tanking everything, and the way he talks is super funny. =P