Rengar or Gnar

they're both fun to play and they both have great stats. just depends on what type of player you are. rengar is an assassin and gnar is a teamfighter.

Both have strong power spikes at certain points in the game. So both are good.

Gnar, I know little about. But from what i've seen he has a good early game, and transitions into a beefy tank for the team. He is fun to play, I just never got super into playing him.

Rengar is a late game assassin fighter. he gets in, bursts someone down in 2 seconds and is durable enough to survive a bit of incoming burst he is bound to recieve.

For fun levels, my vote goes to Gnar. Even though he is much harder to play out of the 2, he becomes insanely fun when played well.

Both require a lot of practice to be good at, so there's that.