Can't Find a Champ To Main

Okay, I understand one-tricking is "overrated" but it's what I want to do. Can you guys help me out? I can't think of any champions that I find remotely enjoyable to one-trick, so I was looking for ideas considering I'm not very experienced.

I like dealing damage, but I also like being RELEVANT late game. (i.e NOT , I played her for a long time and she's too squishy and isn't relevant late game.)

I don't care for being support/tank, both aren't my thing. I am open to anything that you guys can suggest. Again, I want to dish some damage out but I want high mobility and some form of outplay potential... (By outplay potential, I mean champs with utility such as , , and so on.) I don't mind being either AP/AD but I really don't want to build bruiser/tanky.