
Devourer udyr is the most common but Echoes & Cinderhulk udyr can both be beastly. He's dead simple Turtle for the shield, Bear to slap them, and phoenix for damage. Just farm , push lanes, and dive anyone who attempts to stop you. If you do go devourer remember to save drag for the 5 stacks.
Shaco is just fun you run around throwing shivs at people, mess with their minds via clones, and place boxes everywhere. He's the ganking jungler / invader. You won't often get much farm on shaco. He's better at farming champions.. Preferably the other jungler. Team fighting is often hard on Shaco so you're better off split pushing. He also tends to fall off hard late game.
Evelynn is just for popping out of thin air and not being seen by wards. She builds Echoes + Rylais into full tank. First clear or two is rather hard and her level 2 invade often gets first blood. She really falls out at late game though. So You have to snowball the team early to not be useless and push for objectives.
Wukong has nice teamfight / engage and is slippery with his w. He also does decent damage with the standard Warrior + BC + Hydra build.
IF you're just worried about strong picks then something like this would probably be best

Mundo is mundo annoying tank that does entirely too much damage.
Graves is fotm and strong in all roles currently. His aoe makes clears extremely fast and the knock back saves tons of health. He can burst everyone and is a hard counter to melee champions.
Elise has extreme burst, can solo rift herald easily, gives plenty of control via cocoon, and can get out of sticky situations with her spider form e. Spiderlings tank most of the time in the jungle and she also has sustain so full health clears early on are common.
Rek'sai has high mobility / map control and is mostly for vision / knockups and tankiness in teamfights. You can lay tunnels and be anywhere on the map at anytime. Build cinderhulk + cleaver into full tank and just annoy the enemy team. It's a teamfight pick imo.
Nidalee has strong play making potential and invades. However, getting her playstyle and early clear route down is hell and it's very easy to mess up. If she hits a spear on someone out of position it's a near 100% kill. She also can just sit in back and heal / poke. This is a character you really have to be dedicated to maining.
Some other good junglers to think about:

Lee Sin is purely about mechanics and abusing his mobility + ult. If you can insec, judge ganking paths, and ward hop efficiently he's a monster. Good Lee Sins 100 - 0 you before you can blink, sustain through the jungle, and seem to be everywhere.
Kindred is about the early game snowball. You get your stacks and use her burst from e and mobility + damage from w+q to snowball. If you don't get your stacks on Kindred you'll fall off and become relatively useless fast. That is, outside of the utility and fight changing potential of the ult. The heal + death immunity can really turn fights in your team's favor.
Nocturne is just a troll (Devourer jungle though). He does assassin levels of damage and some how always manages to be within ult range to turn fights by bursting your squishies when you least want him there. His ult also mind games opponents. They'll get the screen effect and back off thinking he's ganking them.
Volibear is somewhere between Udyr and Mundo. He is a tanky fighter with plenty of damage and control. The passive lets you live through some utterly stupid decisions. As for his kit in general it's kinda boring you get off a auto, pop his ult, flip them, and then bite them for a rather large burst. He's great at diving, and has relatively decent peel considering the cooldown on the flip.