Whats the best jungler right now (not in win rate but for fun)

your question is circumstantial to your type of play. but if you want something difficult and different, try lee sin. be aware that it's basically impossible to carry a game as lee sin if the game is prolonged.

is a very fun champion. He's easy to play but hard to master. He multiple different play styles and builds that are viable for different situations. Is also fun if you like doing different combos against your opponents.

Lee sin or shaco

Nunu or Hecarim are both junglers I consider just really fun to play. It’s really great to build a massive snowball and flank someone at river. People will run from your snowball like crazy or drop their flash or whatever they need to do. On the other hand Hecarim with a nice speed build is fun because... you play as a freaking horse and you go super fast like a battering ram. Only if you like those types of play styles though.