Hello all! If youre reading this you are more than likely wanting to play gnar in the top lane. Ive spent a lot of time playing gnar and i believe this guide will give you everything you need to know about our ancient yordle friend :)
Gnar is a champion that has a variety of ways to be played but this is one i found most effective. feel free to mes around with this build and experiment as you find fit.

Runes on Gnar differ from player to player. instead of armor or mr quints you could do life steal quints if you'd like as well

Statik shiv on Gnar is a great item. It boosts Gnars strengths and is a great first item. The statik shiv adds movement speed, crit chance, and attack damage to Gnar making him hard to kill in lane.

Mercury Treads are another crucial item. Gnar is a highly mobile, kiting machine- anything to help keep him moving is a great item to have on Gnar. I also highly recommend distortion on your boots to keep your tleport and flash on a low cool down as gnar is a great split pusher and also can do hefty damage to turrets.

Randuin's Omen is going to be your real first tank item. not only does it give you great health and armor but also the active slows nearby enemies, again giving our lil' mobile mongrel an edge on his counterparts.

Spirit Visage is your second tank item. It gives a large health boost as well as regen and magic resist. And as if this weren't enough, it gives 10% cool down reduction which helps Gnar cut down on his lengthier cool downs while in mega gnar form. (Note: between merc treads and Spirit Visage, you'll now have enough magic resist to comfortably go against the opponent's ap carries)

Warmogs will be the last item of the core build.

Final items- there are many ways to go for Gnars final item. if you need another tank item i would suggest either Frozen Mallet or Sunfire Cape (note- do not get sunfire in place of randuin's as first item). As for offensive oriented items i would recommend either Essence Reaver (for extra cool down reduction and attack damage), Trinity Force (for extra kite ability and a small boost to attack damage), or Last Whisper which i would only recommend if they had a rather tanky team.

Some Gnar players will max Hyper (w) first as oppose to Q, but the reason you should max Q first is due to gnar's fantastic range compliment spammy use of his Q ability, so you can poke your opponent out of lane or poke him to the point where you can all in him and win with ease!

As stated in the previous section, Gnar has great range, and also does a surprising amount of damage at all stages of the game with his Q. So first try your best to consistently poke and harass with your boomerang.

Next you'll want to set yourself up to do maximum damage (unless you're confident in your dueling ability, stay away from dueling an opponent till lvl 6). After poking ready your rage bar so you're ready to transform to mega Gnar at the time you desire. when you're ready to go in E or hop on a minion when the ability is blue towards the direction of your opponent. then try to ult them into a wall or turret (fighting near these points gives you a large advantage in an all- in scenario).

If you knock them into a wall or turret, the enemy will be stunned for a short while. Use this time to charge your next attack, wallop (W). the target should almost be out of the ultimate stun when Wallop hits them. Wallop again stuns the enemy for a second allowing for free autos, and boulder throws (Q when in mega Gnar). if they run away use your boulder to provide slows on hit for an easy kill.

when farming with gnar make sure to use your hyper stacks to your advantage. After landing your boomerang on the same minion, monster, or enemy a 3 times, the next Q or basic attack will do extra damage to that unit as well as boosting Gnar's movement and attack speed for a short period of time.

Also to keep competitive farm numbers, use a constant combination of your Q and auto attacks to quickly raise you creep score.

When team fighting, stay outside of the enemy teams attack range until your rage bar is full. once youve met maximum rage Hop into the fight and ult the enemy team into a structure after that continue to provide cc with your boulder toss.

Pros:
-Strong at all stages of the game
-Great mobility and kite
-Can be built to many different play styles
- 6 skill champion
- provides lots of cc great for team fights and ganks
cons-
-somewhat lengthy cooldowns
-hard to control rage bar all the time
-highly vulnerable to high cc or lock down teams/ champions