PROS
+Good laning phase
+Can lockup entire enemy team with GNAR! + Wallop
+Great mobility and kiting as mini gnar
+Great AoE dmg as mega gnar
+One of the best ultimates in game
+Doesn't use mana
+Is a yordle

CONS
-Squishy as mini gnar
-Low mobility as mega gnar
-Failing initiate will usually result in your death
-Controlling you fury is quite hard, so transformations may happen at the wrong time.

I always take Hyper first, as it gives great poke early in the game. however i max Boomerang Throw first for long range poke. Always save your Hop for escaping ganks early game.
The mega gnar burst combo (E Hop -> R GNAR! -> W Wallop -> Q Boulder Toss)deals huge burst damage even to tanks, and stuns them for so long they cannot respond. Suprise your enemy by hopping in with E, ult your enemy to the wall for stun, use W for even more stun, and slow them with Q. Then, if the enemy is on low hp, just pop Dubstep Ignite to finish them off. Also, if the enemy manages to escape with low hp, and decides to recall under his turret, you can just throw a boulder to kill him ;)

The way i prefer to play Gnar in lane is to go aggressive, unless my opponent counters me. The reason i like to play Gnar aggressively, is because escaping ganks is quite easy thanks to Hop and Hyper, and also because Gnar is ranged, he can safely harass the enemy toplaner. If the enemy decides to attack you, kite him by stacking Hyper on him. The speed boost from Hyper allows you to stay at a safe distance from the enemy and dodge things such as Riven's Broken Wings.

MEGA GNAR

Usually when you are about to transform, you'll want to bounce next to the enemy with Hop, and land your mega combo on him. The mega combo is quaranteed to get you a kill against opponents such as Ryze and Riven. However, you aren't going to be going in for the kill everytime you transform, only when the enemy is in a good position for you to land your combo. Mega gnar has great waveclear and AoE unlike mini gnar. If i have enough gold to buy and item, i go b after quickly clearing the wave as mega gnar.

The interesting thing about gnar is that he transforms from a squishy, mobile short-range fighter to a meelee tank with less mobility but great CC. When a teamfight is about to begin, INITIATE IF YOU CAN. keep an eye on your rage, and if you are near transformation, position yourself in the frontlines and use E to bounce a long distance, into the enemy team. Use your ult to lock up as many enemy team members as possible, and make sure to aim for the walls for stun. Follow up with W, Q and then whack them in the face as your team finishes them off.

GANKING
Gnar can be one of the best or worst gankers. Lets say you are on your way to gank mid. In order to gank successfully, you need to have near full fury, so that you can transform. jump on the minions to bounce and ult and W the enemy. However, in mini form, you have very low gank potential. You should only gank in mini form if you are fed or the enemy midlaner is low hp or in a good position to gank.

-You can force your lane opponent out of the lane by constantly poking with autoattacks and with Boomerang Throw once he falls back to under his turret.

-If you get ganked, use your E Hop to jump onto the enemy jungler for a bounce, traveling a greater distance.

-In mega form, you are much less mobile. Be careful of ganks.

-When a teamfight is about to break out and you don't have enough fury to transform, poke the enemy from long range with your Boomerang Throw to gain fury before the teamfight erupts.

-Use Boomerang Throw to check bushes.

-You can use your ult GNAR! to "escape", by showing enemies away from you.

Always get Blade of the Ruined King first. It gives you great chasing potential and helps you stack your Hyper, aswell as giving some attack damage. After Blade of the Ruined King you should always get Trinity Force, i dont think i need to explain why. Then get either Randuin's Omen, Spirit Visage or Warmog's Armor. I usually get Warmog's Armor first, and then build Spirit Visage and Randuin's Omen. Health items are great for gnar, because they not only grant survivability, but also increases the damage of Hop/ Crunch.

WOMMBOO COMMBOO!!
These champions work great with gnar in teamfights:

Cassiopeia-her ultimate Petrifying Gaze works amazingly well with gnar ultimate GNAR!. first throw your enemies to the wall, follow with Wallop and then cassiopeia stuns/slows them all even more with her ulti (or the other way around), which is a crazy amount of CC. Also because cassiopeia can deal area damage it works well on the stunned enemies.

Wukong-his ultimate Cyclone works well with gnar aswell. Just like with cassiopeia, stun them and wukong can knock them up for even more CC. With his ulti he also deals area damage which works well.

Teemo-How well this works depends, as it requires good positioning. Ask teemo to lay shrooms Noxious Trap near a wall in a good location, and if you can successfully ult the enemies INTO the shrooms, AND the wall, they will continuously take heavy damage.

Orianna-After Orianna uses her Command: Shockwave, bounce in with your E and ult the enemy team when they are stacked. You can also bounce in first and orianna can use her ultimate after, but to get the most of your ulti, orianna should use her ulti first. Great CC.

This is just a small guide, as i am not a great writer and also, again, its my first guide.
I would appreciate if you had any suggestions on how to improve my guide :)


GL HF!