Hello and welcome to my Season 6 Warwick guide. WW is one of those champs that can do wonders and yet they are so simple. Also, he has a variety of builds, some more, some less effective. The build above should be effective most of the time, if not, mix things up, you might prevail.
Let's begin shall we?

Pros:
Easy to play
Great jungle sustain
Instant and strong CC
Good damage
Tanky
Can outduel almost anyone mid-late game
Cons:
QSS is a pain
Easy to outplay
Can be useless if starved of farm
Kiting is a nightmare
Ult can be stopped by any hard CC
Ult is your only real CC

Why do I run the setup above? Simple.

First of all. Attack speed reds are always good for an autoattacking jungler, plus that one crit can save your rear. Don't even get me started on how many times that one crit helped me.
Scaling HP yellows give you up to 216 HP at level 18, that ain't little.
I get my specific mix of blues because 40%CDR is always good on WW. scaling 10% plus the rest put scaling or flat MR, depending on the matchup(scaling should always be superior).
Armor quints some might find to be strange, but hear me out. Imagine a Lee Sin invading you. Most likely it will be at your red(99% of cases their Lee invaded there

Your focus should be on Thunderlord and a bit of sustain and tankiness. A change in the masteries if you want can be to go for Intelligence(45% CDR). I personally prefer Precision(Armor and Magic pen) because WW has so much mixed damage. Also, Bandit can rack in a lot of gold, but I prefer Dangerous Game because i won't often get the opportunity to use it. But if you lane with a melee champ,go for it(Imagine Heart of Gold,but in a mastery)

I don't think i need to say much. Classic and still good.

All the info you need is in the notes, but i will explain specific items here:
Warwick is an exceptional duelist, so I go for the true damage + reduced damage from the enemy. That + Red, ain't no one getting away. Devourer has always been good on WW, just synergises well. Some go cinderhulk(Then you're just useful for your ult) or warrior(Again,it falls on your ult to do something), but devourer is superior
This item is so underrated it is just stupid. Attack speed, MR, 42 magic damage on hit, MR shred, AND IT IS PROCCED WITH YOUR ULT(expect at least 150 bonus damage on ult if we count in the MR)
The synergy is just amazing. You can't itemize properly vs such a combo. Also, rageblade gives decent waveclear
A classic, needless to say much. The stats are just perfect for him. After the nerfs though,i prefer Gunblade + Rageblade, but if their team is tanky as heck, build Botrk, you won't regret it.
Your first ult hit will proc the Sheen effect, and also you have low CD on your Q so you can proc it often. Basically, Triforce for damage, Gauntlet for Sustain and CC. Go for Sterak if you buy one of those two. Sheen effect scales with BASE AD
Classic tank items. Frozen mallet for permaslow, HP and a bit more damage, Spirit Visage for more sustain and MR(Stacking it isn't too bad either, good vs heavy magic damage teams), Frozen Heart for sustain, tankiness and is also good vs AD carries
Personally, I avoid boots because i have E and an instant gapcloser, but if you can't catch up,put it in somewhere

Farm, Farm, Farm. Don't gank unless it a 100% guaranteed kill. Dont force invades unless their jungler is weak and/or their jungler is far away. Level 6+ look for ganks whenever your ult is up. Whichever lane you gank successfully, go for Dragon/Herald, whichever is nearer.
Also, GET DEVOURER ONCE YOU HAVE THE CASH.
A good idea is to camp and push mid early to motivate him/her to roam while you stack up

Prioritize objectives and go for skirmishes, less people to stop your ult. Push lanes with your ADC and W

Still prioritize objectives,WW is great at taking them, since his ult can supress their jungler while you smite Dragon/Baron. In teamfights, ult their most dangerous target(ADC, Assasin, Mage) once they get out of position. You should be in the middle, closer to the front, but not in the front, you aren't the tank.

This should be about it for now. I am not very experienced with making guides so any suggestion is welcome. Nevertheless, this is it for my 6.1 Warwick guide, I will expand/change things up if something changes(I've heard that they plan on nerfing Thunderlord). Now, I bid you Farewell from the Frost Wolf, S. Yukinari