First off i'd like to say this is my first guide ever on mobafire. I used this guide in a few games and thought it was good enough to post on mobafire. I am still very inexperienced in guide making so please comment and leave suggestions.(most of the sections will be short)

Pros

+ Very tanky
+ Bola strike snare/slow good for starting ganks
+ Receiving Assists procks Bonetooth Necklace
+ Good Damage early game
+ His ulti is good for catching up to enemies
+ Very Annoying to play against
+ Great Jungler

Cons

- Not as well with ranged units
- Not as much CC as any other "Tank"

As of for runes, Flat armor and magic resist will help alot in the early laning faze considering that you'll be jumping onto the enemies. The MS Quints will help catch up to foes or get a quick getaway. The extra damage will make it so that harassing hurts more(the more damage the better :D)

For the masteries using your own tank masteries will fit perfectly fine with tank rengar.(i don't know what else to say :/ )

For boots i recommend getting Mercury's Treads, If there isn't much cc get ninja tabi.

For Tank Rengar's Core items get Warmog's Armor, Force of Nature, Randuin's Omen, and a BoneTooth Necklace.

The last item could be an anything, i just use atma's for more damage.

As of skills, i recommend getting bola strike first, its great to harass from a range and will be useful for catching enemies or running away. At level 2 get his w, the bonus armor and mr will be useful for sustaining in the beginning. Get his q at level 3 so when u need to jump at them u got more damage. The rest of the leveling is for what you think is needed in your lane. I get some more levels into his bola strike so that they won't be able to get away that easily. While leveling his bola, I also level his w for somemore resistance. Later on i max out his q later on for more damage output.

-I'd say that exhaust is the way to go when laning at bot as a tank.

-I also get ghost but flash is exceptional also.

-Ignite would be ok but i only get it if my lane partner doesnt have ignite.

-Teleport i wouldn't recommend getting but if you know you won't do as well staying in lane then get teleport so u can go back into a lane quick.

-Other spells i wouldn't recommend using at all for him unless your partner wants it

In conclusion i'm pretty sure the description of this guide(all the categories)have been written wrong so feel free to comment and i'll try to make it better with your suggestions. This is my tank guide and hopefully its a good one ^_^.