Obviously WW jungle, I mean the champion is boring to play though...
least that is actually fun to play could be Darius

I never really play him, but when I did it was pretty fun ^~^
About highest mechanical, I would say Kalista now, she is extremely fun to play though she is kind of weak, but honestly, with her shit range and low damage, it's really hard to do good x_X
Zed/Syndra are pretty fun and can carry well :^)
On the ryze thing, In low elo he is kind of easy, since people just have no idea in general how to play against, I played against quite some in low elo with him and they just tank his poke 24/7 and take a melee tank against, but really he can get shut down pretty easily if you know how to play against and it can be extremely hard to master for multiple reason :
=> Low MSe
=> Really squishy against a lot of early game all-in ( or vulnerable.. )
=> Damage pretty low early
=>Needs to farm to be efficient
=> HIS RANGE IS BASICALLY MELEE Q_Q
=> Get outdamaged and outtraded by closely everyone early ( just take pant and make him cry by only pressing Q seriously.. )
=> Can really suck in teamfight if you misstime your R :l I mean his AoE spells are really what make him a beast late game, so if you fuck it up or ennemy is way too split, your farm just might not be really worf it.
I am not a really good ryze player, but it's one of the only I play top lane though :L