After all the nerfs they have on Irelia(Rengar), the triple Q is sadly not an option now. However, I still found assassin Rengar quite fun as I'm killing their Jinx or Vayne before they even auto-attack once in a team-fight.
P.S. Do not completely copy the build for every team comp, it defines how silver someone can be.

Starts with Q if not invading, E for slow if a wild mid appears, bla bla bla pretty much common sense for Rengar junglers. After the nerfs, your heal is not that great when you have more than half, and the bonus damage would really help you with big wolfs and wraiths at first, therefore try to use Empowered Q more often.
Most of the times your opponent jungler starts with blue even for some lee sin who are surprisingly mana-less(duh) which makes blue with only 10%CDR almost useless, stealing their red would dramatically reduce their ganking ability and puts you at a head start for exp.

Sword of Divine is pretty underestimated for the current meta, an ad assassin very often find the enemy carries kiting them and are they only have 3-5 auto-attack worth of time to kill them or damage them enough to force a disengage from the team-fight.
For example a Xin Chao can really hurts when all 3 attacks from his Q crits, not to mention the 100% attack speed bonus which make the 3 strikes to go at almost cap speed (2.5 attacks per sec), most AP or AD would panick-flash or just succumb to your superior AD power.
Plus, with your ult and ghost, you are pretty much jumping from nowhere except for the mark they see at the last second(which is probably not gonna help their ad escape your kitty claws)

Pros:
-You are killing their carries before they have a chance to do anything in a team-fight, how much more do you need?
-Many Riven or Yasuo who only build a Guardian Angel for tankiness would find their revive to be merely useless.
Cons:
-Low sustain(which is what assassins should be).
-Your early game is very weak for your only health comes from trinity force.
-Team-fights don't win themselves even when their ADC or APC is gone, a garbage team would leave you fight someone with a quadra-kill at the end with his/her teammates shouting
/all PENTA!!!