Fiora,Lissandra,or Zyra

If you want a challenge go with Lissandra or Zyra. If you want easy broken champ then do Fiora.

zyra is the only one probably free from the nerfbat

Lissandra, she goes top, mid and even bot if you can play it right.

She's versatile, and has utility even if she's behind.

Lissandra is far and away the most fun, as well as the most flexible. Fiora's kit is kind of dull, and was slated for a rework eventually, so I would avoid her. Zyra is ok, but she just isn't my style so I don't know how to comment on her. Lissandra can either build tanky or super burst. She has a ton of CC, and can go everywhere, except ADC (not quite sure how well she jungles anymore, since I haven't tried her since the preseason came out).

Lissandra is way more fun in my opinion. I love her E claw that allows her to teleport over walls. But its really up to you.