I second
Zac. I've played a lot of him (Level 5 Mastery) and he's in a very good place right now. However, he has a fairly high skill cap compared to other junglers. His passive (Cell Division) allows him to regain a lot of his health quickly and clear jungle incredibly fast, but the algorithm for the blob placement always brings the blobs closer to the enemy, meaning you might have to risk it all to get that health back. But on the flipside, Cell Division's death passive is great fro surviving teamfights and distracting enemies. And if one of your teammates is carrying teleport and keeps an eye on your bloblets, you're functionally immortal until you reform. He also great engage with his E (Elastic Slingshot) and R (Let's Bounce!), and deals max health damage with his W (Unstable Matter).
I also recommend
Kindred (Level 5 as well). They have gotten nerfed recently although the new champion coming out (possibly Sorag) has caused Riot to update their minimap code. This means Kindred's buffs will only be visible to them instead of to everyone in the game, something that they were plagued with from release. Kindred has range other junglers simply can't match, which means your ganks will be especially potent with Q (Dance of Arrows) and E (Mounting Dread). The newly added slowing effect to W (Wolf's Frenzy) makes kiting and chasing a breeze, and you can hop over lots of walls with your Q. And your R (Lamb's Respite) can turn impossible 1v1's and teamfights into a walk in the park (not to mention it makes tower diving very easy).
Finally, although he has fallen out of the meta_ hard _recently, I'm a huge fan of
Skarner (Level 5 Mastery, too!). His kit makes getting rid of him incredibly difficult and his R (Impale) allows him to make game-changing picks and suppress a carry for 1.75 seconds! His passive (Crystal Spires) gives him a huge edge in the jungle and his E (Fracture) gives him the chase-down and peel that makes Skarner a tough bug to shake. Anyone who stumbles onto you when near a Crystal Spire is doomed the moment you give chase. Combine this with the attack speed from his Q (Crystal Slash) and shield/movement speed from his W (Crystalline Exoskeleton) and Skarner is a scary scary scorpion. However, he suffers from a strange playstyle and no long-range abilities (this could be why he fell out of the meta), but if you learn him he is well worth the time and effort.
Also, if you're feeling like some weird junglers, might I recommend:
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Taliyah
She has insane gank and lockdown potential with her passive (Rock Surfing) and her R (Weaver's Wall), but her skillset is very hard to use properly and missing your W (Seismic Shove) ruins your entire combo. That being said, Taliyah is a natural mage jungler that can solo carry if played correctly.
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Zyra
With the changes made to Zyra's passive in the big mage update, she's back and better than ever in her natural habitat. Her passive, Garden of Thorns, means her plants can leash monsters for her and she'll take little to no damage. Her insane peel and CC from E (Grasping Roots) and R (Stranglethorns) makes Zyra a threat from the word go. However, she has the lowest base health and movement speed of all the champions, meaning you will need to play your cards right to make the most of her.
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Aurelion Sol
Aurelion Sol is a strong jungler thanks in part to his passive, Center of the Universe, which deals constant damage and executes under a certain health threshold. Sol gets very tanky in the late game too, and his E (Comet of Legend) combined with his Q (Starsurge) makes him a incredibly potent ganker. His R (Voice of Light) is great for peel and CC and can net long range kills during teamfights. With the recent changes to his E, Sol looks to be stronger than ever when it comes to roaming.
I hope you find who you're looking for!