Which champion gives you goose bumps in terms of "this is me on the summoner's rift". Like you feel completely connected to the champion's lore, kit, what he or she or it represents and what he she or it stands for.
For me would be Quinn. I've always loved playing ranged characters in video games. I love her abilities and the fact that she's not the most popular champion, at least wasn't before pre-season 6. She lost her brother and is now teamed up with Valor, and she sees the same qualities in him as her brother had, so they have a special bond. And her new ultimate is badass, let's face it, permanent movement speed boost to roam the map very fast.
Which one is yours and why?