You'll probably want to try an assassin. Fizz is pretty much always good. He has a very low skill floor (you can make flashy plays without much practice) yet a decent skill ceiling.
Other champions I would recommend: Rengar, LeBlanc (both pretty straightforward to play)
Champions I wouldn't recommend (but you might like anyways): Kha'Zix (the isolation mechanic can be very inconsistent and hard to master), Talon (tends to fall off meta and suck), Akali, Ekko (both are being played more as bruisers than assassins and Ekko is IMO a bit hard to pick up), Zed (he's a good pick, I just can't come to terms with recommending him to anyone)
Side note: Assassins are being revised during this preseason (december 2016/january 2017) with some minor updates happening to a particular bunch (to be defined possibly after worlds).
All very good choices. If your play style is most like ADC try champions such as Kindred and Graves that are mechanically like ADC but are more burst reliant.
Other champions I would recommend: Rengar, LeBlanc (both pretty straightforward to play)
Champions I wouldn't recommend (but you might like anyways): Kha'Zix (the isolation mechanic can be very inconsistent and hard to master), Talon (tends to fall off meta and suck), Akali, Ekko (both are being played more as bruisers than assassins and Ekko is IMO a bit hard to pick up), Zed (he's a good pick, I just can't come to terms with recommending him to anyone)
Side note: Assassins are being revised during this preseason (december 2016/january 2017) with some minor updates happening to a particular bunch (to be defined possibly after worlds).