Flat AD Marks should be used over Armor Pen, as Electrical Surge bonus damage is increased via AD but deals magic damage so is unaffected by armor pen.

Also, on both of your builds you run Ignite but do not get the point in Summoner's Wrath in your masteries. I assume this was just accidentally overlooked?

runaan's hurricane has good potential but de facto DPS from it varies greatly. The secondary attacks can't proc the on-hit damage they can only count towards stacking it. It is a really good item for team fights that are clustered together via AoE CC ultimates like if you have a jungle Amumu or Sejuani on your team. Most of the time though you should be orb-walking, kiting, and repositioning in between attacks. The current meta involves you destroying a tank line / whoever is diving you faster than the enemy AD carry can destroy your front line. Because of this, most team fights are spread out over a longer distance and opponents are too far apart for one another for runaan's to hit multiple targets. When it comes to single target damage, Phantom Dancer is far superior especially considering you have IE in your build. A previous comment mentioned that IE without supplemental crit is bad itemization and I would have to agree.

I also am a firm believer in the fact that Blade of the Ruined King is more cost effective and does more damage late game than Bloodthirster. the math speaks for itself to be honest

"focus the enemy carries before all else, and you're set." this is bad advice to be blunt. An ADC should generally be attacking the highest priority target within range that they can safely attack and more often than not simply the closest target.

The nashor's tooth also makes zero sense to me. The AP does not increase your damage by that large of an amount and Kennen;s ability use is limited more so by energy management than cool downs or anything else. Statikk Shiv, Blade of the Ruined King, Phantom Dancer, Bloodthirster would all do more damage.

the majority of your guide is good and has plenty of coding and whatnot. just a few things I strongly disagree with

interesting guide! I started to play him again (long time no played him), and started with ADC, and has a very good potential, seriously. I would have to check my runes, don't know really if I got the correct ones, but he's an hard oponent!

I also use seekers armguard for early armor and harrassment damage for q and w. Then i build an early avarice blade (great for farming) and turn it into static shiv later. No bloodthirster or IE, just BORK since it exploits his super fast AS.

Alright home from school, so I'll test out both the PD over Nashors, and the different marks. I'll put my opinions on them up tomorrow or so. Thanks for the feedback guys!

If you get Infinity Edge, you gotta crit.

If you get no Phantom Dancer, the crit is too little.

You will need to replace Nashor's Tooth with Phantom Dancer, it will really increase your AD damage output.

I already read your item explanation for Nashor's Tooth, if you wonder that.
I am not convinced :P

I just picked up Kennen after trying critical build Garren, I'll be more than happy to pick up and test your build

How coincidental. I literally just finished reading your 10 commandments. I'll test them out tomorrow. It's late and I'm tired. Been writing this all day. Thanks for the comment though.

Armor pen reds are wrong. Flat AD please. Hybrid pen is a possibility. Kennen deals no physical damage outside of his autoattacks.

Thanks a ton for the comment and feedback! But yea, I tend to stay in lane until I have around 2400 or more, avoiding ganks is quite easy if your support knows what he's doing, and if you play it right, you should have about 2-4 kills on your first back. That's just me though, I'm sure beginners will beg to differ, but hey, to each his own right?

damn that's an ambitious first back haha. I don't adc much but ill be lucky to get a bf on first back. Nice build otherwise, love runaan's so much!

Yea I was thinking about it but it's my first time around, so I'll work out the kinks. Thanks for the feedback though!

I would consider Blade of the Ruined King in your hybrid build, at least as a situational item. Kennen has naturally high AS, so he'd benefit well by using BoRK against high HP champs.