Easiest Junglers, Ever
I made a thread kind of like this one a few days ago (at the time this was written) and I'd dramatically change what I had written.
Jungler #1
Warwick: FIghter
Warwick has a lot of sustain when fighting due to his trait, Eternal Thirst. This causes Warwick to deal a small bit of magic damage with his autoattacks and heal for that same amount. This will stack, in other words, increase the amount of healing gained. Although it doesn't completely heal you through all damage you take, it greatly helps when fighting jungle monsters. His Q, Hungering Strike, is a life steal ability. What it will do, is it will deal damage to enemy, and then heal him for 75% of that damage dealt. Very useful when dueling another champion. His W, Hunter's Call, increases his and all nearby ally champion attack speed for a certain amount. Warwick's allies gain half the attack speed he himself would get. His E, Blood Scent, reveals nearby enemy champions that are below half health and increases Warwick's move speed by a certain amount, which makes him very good at chasing low health targets. Finally, his ultimate, Infinite Duress, locks down an enemy champion for a few seconds, and dealing damage over that duration. Overall, Warwick has a simple kit and not a very hard champion to use, and is also only 450 Influence Points. I recommend skilling up your Blood Scent first for maximum chasing potential.
Jungler #2
Nunu: Fighter, Support
Nunu is a fantastic jungler mostly due to his Q, Consume. Cannot be used on champions, but can be used on minions and monsters. It will deal true damage to them (simplified to: a lot of damage :P) and heal him for a certain amount. It will also grant him a buff when he uses it on certain jungle monsters. Elementals (Brambleback, Blue Sentinel) will grant him increased health and size. Animals (Murk Wolves, Raptors) will grant a small movement speed IF he kills one with consume otherwise you won't get the buff. Other Monsters (Krugs, Gromp) will grant him additional magic damage equal to a certain percentage of his maximum health. Nunu's trait, Visionary, lets him cast an ability free after 5 attacks (autoattacks) so he can be very mana efficient. His W, Blood Boil, slightly increases his and an ally's movement speed, but drastically increases attack speed. This can help you activate Nunu's trait. His E, Ice Blast, is a missile type ability (it will home to its target) that will deal damage and drastically reduce that enemy's attack speed and move speed for 3 seconds. Finally, Nunu's ultimate is Absolute Zero. It is a channeled ability (has to be cast over a certain time and can be prevented) that will deal very high damage based on how long the ability has been charged. During this time, enemies standing within the area have their move speed reduced by 50% and attack speed by 25%. This ultimate has to be channeled over 3 seconds for its maximum damage. Although Nunu is considered part support, you are wasting half of his potential if you aren't jungling with him. Nunu also isn't the best champion for dueling because he only has one ability that hits enemy champions. However, he is great with chasing down kills with his ice Blast becuase of the massive slow. Nunu also isn't very hard to use, and is also only 450 Influence Points. I recommend skilling up Consume for getting the best out of the minor buffs and and damage.
These are possibly the easiest jungling champions in the game, and don't worry about feeling like a noob when you jump into these guys and really like one (or both) of them. They are used in ranked matches, tournaments, and pro play in general.
Honorable Mentions
Amumu
Udyr
Xin Zhao
Fiddlesticks
Master Yi
Nocturne
These are also great junglers, but they are a bit harder to learn than Warwick and Nunu.
If you are a newbie, comment down below if this helped or not. If you are not new, comment down below who you think are the easiest junglers.