Rengar is a Jungle/Top champion who has a huge burst potential.
He can burst any squishy with is Thrill of the Hunt and get out with his post-stealth movement speed bonus.
He is usually played as an assasin and his kit helps him in that role.
Here is a quick guide on how to play him !

greater mark of armor penetrationArmor pernetrations are strong on him cause it scale better into late and allows you to do as close as possible true damage. It fits well with his core build.
The lack of Ad in his early can be a problem for early trades in the jungle and clearing might be a bit difficult if you aren't use to.
Cooldown reductions runes give you an extra 10% to the early game and combined with his build you get the 40% cdr. It allows you to ult more often and it ends up to a kill almost everytime.
Armor helps you vs the monsters and basic attacks.

It's the best runes set up.

The masteries tree is made to help you with the clear and give you bonus damage.

-> It's the only mastery i found useful with the Stormraider's Surge ( ).

Since the nerf of fervor of the battle, the best mastery is the Thunderlord's Decree because it synergize well with your combo and gives you an extra burst on tankier target.

Armor Penetration items are the strongest on Rengar cause they gets you closer and closer to true damage.
Even if the black cleaver gives armor penetration it gets you overcap in CD-R and it needs to stack for the max armor penetration so it isn't worth gold.

Sustain items (lifesteal) allows you to stay in the fight longer after you bursted their adc. It helps you in duel and you can heal back after the fight without having to back.

Cooldown reduction With this build you'll get 30% CD-R what you want it's 40% to ult as often as possible. You will probably get blue buff if you hard carry and get your extra 10% in that way or you can buy lucidity boots instead of mobility ones. Do that if you can't have or steal a blue buff.

-> I max it over -> because it gives a lot of damage and you don't need much resistance as an assasin.
-> It's the spell you'll use the most and will do the most damage you MUST max it first !
-> It's your ultimate and an amazing gap-closer u must max it as often as you can (At level 6/11/16).

Q

W

E

R

Once you have the core build you might be allowed to "One Shot" with this combo:
*)Have full ferocity.
*)Activate your empowered and leap on your target.
*)As you are leaping,mid air,activate your ,which will apply when you land
*)At the same time, keep your cursor on your target so you can use to hit them before you land
*)Activate your and ,once landed, at the same time for the finish.

You can use your first in case they have an escape ( as Ahri ult, Graves dash or something...) they will get snared and you will deal less but a 100% chance of burst. To do that just forget the before the leap and do the other steps but this time you'll get !

Even if you are an assasin don't forget to play WITH your team. Don't suicide or go too deep where your team can't back up (aka the funtain).

You want to have almost all the time 5 stacks of ferocity so you can get a good ultimate.
You can stack on close camps such as crab or raptors.

Rengar have the possibility to attack reset with his .
To do it you just have to wait until Rengar do the damage with his basic attack and cancel the animation with your .

You should only use or or
for farming, the first gives you extra damage and attack speed when the seconds heal you and gives you extra armor and magic resist.

As Rengar you can farm up to your 6 and it will be totally fine and safer cause a gank with your ult is a 80% chance to kill. The cons of farming up is that you will expose your team and let them down facing ennemy's jungler ganks. Even if it's safer.

You can still do a cheese by taking your bolas lvl 2 and ganking (the top lane is the easiest) with 5 stacks of ferocity, u get in the bush when the wave is pushed or sneak behind the ennemy top laner. When you are in the bush use your passive to jump and him and mid leap empowered bolas them and deal most damage you can if you are both on him you will kill without having to burn flash. If he don't die and flash out you can simply flash after him (don't waste 2 summoners or YOU flash or YOUR TOP LANER flash).

Of course you can gank with Rengar pre 6 but without bushes and ult he has no real gap closer and his bolas is easy to dodge so gank only if you are sure at 100% you can get a kill.