Since I started playing I've had several favorite champions.
When I was just starting I used to main Warwick. I really enjoyed the simple mechanics it takes to play him. You just press R on them and bum..., they're dead.
As more time when by, I switched my main role to AD carry, since I started enjoying their mechanics a lot more. Things such as orb-walking and kitting. By these days I played mainly Kog Maw. Its is still one of my favorite champions nowadays, but I came to hate my dependence in my teammates, as, at least on my level (Silver, and yes, I know I suck
) no one protects the ADC. People just dive the enemy team's ADC and that is it. There is no protection whatsoever, not kitting the enemies trying to kill your team's most important player, in terms of damage.
Because of that I started playing more mobile champions, such as Corki, or Ezreal. It really improved my game, since I was now able to escape a lot of hairy situations. I can't count the times I just kitted the enemy Udyr or Shyvana to oblivion.
More recently, and since I started getting better at orb walking, I main Jinx. Her kit is really versatile, as, despite not having any escapes, I have hard CC, in her E. Since then, lots of pentas were made. The passive helps a lot in doing that