I'll start off by saying I have nothing against full AD or AP Kog' Maw, I've played both and have had a lot of fun. This build is my personal preference and nothing more. What this build lacks in departments like lifesteal it makes up for in attack speed and overall damage. If you're going up against a tanky team, this build will cut through them like a hot knife through butter. This build isn't for everyone and if you feel you fall into that category then I highly recommend you try full AD or AP Kog' Maw, he's my favorite champ and a lot of fun to play no matter how you build him.

He's a video of this build in action with my favorite support to work with, Blitzcrank. This was back before I started taking heal and used exhaust which I still occasionally take. You get the idea of the damage and the fun that is to be had with Kog' Maw.

If you'd like to check out more of our video's they can be found HERE or you can check out our stream by clicking HERE!

Pros / Cons

Pros:
Great mix of range, speed, & damage
Has a good slow when used right
Melts tanky teams
Is a problem late game

Cons:
Very Squishy
Slow early game
Tends to get focused

Runes

Marks:
While this build does both physical and magic damage, you're going to find you do more magic damage. Greater Mark of Magic Penetration gives you some good magic penetration along with your Greater Quintessence of Magic Penetration and getting your Sorcerer's Shoes, you should notice your Bio-Arcane Barrage doing some damage. Not sure I would suggest taking anything other than these for you marks. I have taken Greater Mark of Attack Speed in the past, I just find you need that magic penetration and that, while attack speed is nice, your attacks need to be able to get through your opponent's resistances. Possibly the Greater Mark of Precision just for the armor and magic penetration. I haven't tried these myself yet, but I could see them working.

Seals:
You can, and I have gone, a few different ways with these. You're going to be bot lane against an AD carry and Kog' Maw is squishy, Greater Seal of Armor gives you the armor you need early to stay in your lane and farm comfortably. I used to take Greater Seal of Attack Speed because more attack speed never hurts and it gives you a little more early game. That being said, after a while I found that that attack speed means nothing if you're getting killed because you lack armor. The last one would be Greater Seal of Replenishment, Kog' Maw is mana hungry, and you will find yourself running low or out of mana. Unfortunately, after playing a lot of AD carries, I've realized that that's what happens early game if you spam your attacks. I'd much rather take armor yellows but if you find you need these, go for it.

Glyphs:
Not as many options here, I not only take Greater Glyph of Scaling Magic Resist with Kog' Maw, I take it with just about every AD carry I take bot. Other than the Wit's End, you have no other magic resist, and you're not getting that for quite a few levels, if you get caught by an AP carry, you could find yourself in big trouble. Now if you find you're not having this problem, I wouldn't recommend not taking magic resist, but if you're set against it Greater Glyph of Attack Speed gives you more attack speed and like I said before, that's not a bad thing.

Quintessences:
Now you may have noticed I took 2 Greater Quintessence of Magic Penetration and 1 Greater Quintessence of Attack Speed, this is just what I take. You could go either way here, but these are the only two quintessences I would take. That being said, I did mention a possibility of Mark of Hybrid Penetration in the marks section, so it would only make sense to mention Greater Quintessence of Precision. I could see the armor and magic pen helping out, I just haven't tried these myself and until I do, I can't say for certain weather they would or not.

Rotation

This build relies on your ability to use all your skills at the right times. The majority of your damage should be provided by auto attacking using your Bio-Arcane Barrage along with your Caustic Spittle. This is going to deal a lot of damage, especially when you get your Malady and Madred's Bloodrazor along with the rest of this build.

The ideal situation is to get a Void Ooze on an enemy and unload on them with Bio-Arcane Barrage and Caustic Spittle following up with your Living Artillery. It's not always going to be this simple, however, it gives you an idea of what you'd like to happen.

The thing I love about this build is that even if you're getting beat early, you can almost always keep yourself in the game. I've had many games where it feels like you're going to a 20 minute surrender, and then suddenly you get your Madred's Bloodrazor and all hell breaks loose. I've had games where I've started out 0 and 7 and seemed to be sure defeats and came back to win and go 21 and 7. This won't always be the case as there are some games you just can't win.

Summoner Spells

THE BREAD AND BUTTER

Heal:
As with most AD carries, I take Heal. Very helpful early especially with the mastery point. This can be a big life saver and sometimes the difference between getting killed and getting a kill.

Flash:
Since Kog' Maw has no true escape, it's almost a requirement to take flash. I can't begin to tell you how many times flash has saved my life and combined with your slow there's a good chance you can get yourself out of trouble.

Surge:
Surge is great for this build and it's one of the few spells I'd take over heal, It helps you secure early kills and continues to throughout the game. Personally, I tend to lane with supports who don't have heals so I almost always take heal, but if I'm with a Soraka or Sona, I might grab this instead.

Ignite:
I used to always take this with pretty much everyone. While it helps secure kills and can be a difference maker, Kog' Maw is on the squishy end and if you're the one trying to tag someone with ignite in a team fight you're probably too close. Kog' Maw's range allows him to stay back and do damage, if you have to get in close to ignite you run the risk of getting demolished.

Exhaust:
Like Ignite, I feel like you have to get too close to the opposing team to use this. This can help you against the other AD carry and can be a difference maker, however, I'd still recommend taking heal and having your support take this. If no one on your team has it and you feel like your team needs it, go for it.

Ghost:
I wouldn't take this over flash but if you feel the need to, go for it. Kog' Maw can always use some speed weather it's getting to a fight or running away from one. It's a personal preference, I just like flash more with the ability to go over walls and getting out of sticky situations.

Cleanse:
I don't usually take this but I can see where it would help, combined with flash I could see this saving your life time after time. Personally, I don't like giving up heal as it can benefit your team more but if you're going up against a team with a lot of CC then cleanse wouldn't be a bad way to go.

Teleport:
I personally wouldn't take this, I could see where you could teleport to get closer to a fight and it could be the reason you secure kills but there are better summoner spells for Kog' Maw.

Clarity:
While Kog' Maw can be mana hungry, especially with this build, I don't think I'd take this. Maybe, if you plan on spamming your Ult and your slow, but other than that, this is probably something more viable for AP Kog' Maw.

Revive:
I could see one scenario where this works. The enemy team is pushed into your base and if you ace them, you can save this game. Your revive is up and you decide to go all out and deal as much damage as possible only to die and explode on them with your passive getting them all pretty low. You immediately revive and finish them off like the true hero you are. While this would be an impressive feat and pretty awesome to do, I just don't see that happening at all, but if it did, I'd hope LOL replay was running in the background.

Promote:
Just like meth, not even once.

Smite:
Dat Jungle Kog' Maw too stronk.

Clairvoyance:
You shouldn't be the one taking this under any circumstance. NO! THAT'S A BAD KOG' MAW!

The Build

Starting Items:
You can go a few ways here.

The first time you go back, you should have enough to at least build Madred's Razors and maybe a Dagger or 2, this should help you out quite a bit in lane.

The next time you back, you should be able to afford a Malady and possibly finish your Sorcerer's Shoes. If you're doing well, you might even be able to buy a Recurve Bow.

Getting close to mid game, you should now be finishing or close to finishing your Madred's Bloodrazor and buying another Recurve Bow. If things are going great, you might be able to build your Wit's End.

By now you should have at least Madred's Bloodrazor, Sorcerer's Shoes, and a Malady. Start working on your Wit's End. If you have that, build a Zeal. It's gonna be a little while before you can finish your Trinity Force the game might even end before you get this far depending how things are going.

-OR-

At this point, you should be finishing or close to finishing your Trinity Force. The next item you should work on is a Guardian Angel. You're probably being focused in every team fight by now, this should help that. If you find you aren't being focused and you just want to do more damage, build a Hextech Gunblade. This is something I do from time to time and if I have the gold and my GA goes down, I sell it and buy a Gunblade. If you get to the point where you finish the build and you have the gold, finish it off with Elixir of Agility, Elixir of Brilliance, and Elixir of Fortitude and if necessary an Oracle's Elixir.

If you find yourself being focused a lot and you already have Madred's Bloodrazor, Sorcerer's Shoes, Malady, and Wit's End built, you might want to go for a Guardian Angel before you move on to a Trinity Force.

When building your Trinity Force I usually start it with a Zeal because of the attack and movement speed. It's also the least expensive of the three options. You don't always have to start it out with this, you can build a Phage or a Sheen, both have their benefits to you. A Phage gives you a little damage and some extra health. which is good because you are on the squishy side. It also gives you a 25% chance to slow enemies. Starting with a Sheen will give you a little ability power and mana. It's passive also works well with Kog' Maw.

Only buy elixirs after you're done with the build, the only one I'd take before hand is Oracle's Elixir if you need it, but you shouldn't be the one buying this. If you need it and people refuse to get it then buy it.

Optional Items

I'll start out by saying that I almost never build anything thing other than what's in the main build. I find the items there are what's best for this build. That being said, there are still items out there that can work with this build.

The first one and only one I find myself building from time to time is the Hextech Gunblade. As you saw in the main build, I do sometimes build this if my Guardian Angel is down or if I'm not being focused. It offers you lifesteal, spell vamp, AD, AP, and an Active that deals 300 magic damage and slows that enemy by 50% (When you remember to use it).

Like I said before, I usually stick to the main build, and apart form building a Hextech Gunblade instead of a Guardian Angel, I don't ever build anything else. The items listed here are things I could see working to either help with damage or be purely situational. If I ever get around to trying these different items with this build, I'll update this section with more information. I could even change the main build, but for now they'll be listed here.

As far as your boots go, I could see where Berserker's Greaves or Mercury's Treads might work. I find the Sorcerer's Shoes give you the magic penetration you need, but if you find it doesn't impact your damage, more attack speed doesn't hurt. Mercury's Treads are one of those situational items for an AD carry. I personally always go with what will help my damage. That being said, if there's a lot of cc on the other team, I could see building these, just not something I ever build though.

Speaking of CC heavy teams, I could see building a Quicksilver Sash. I might build this if I find myself only dying because I get caught by a stun/snare as the active will get you out of it. The magic resist doesn't hurt but the reason for building this is it's active. If you do build this, I'd build it instead of the Guardian Angel. I don't think any other item would be worth giving up for this.

As this is more of a hybrid build than anything else, it would only make sense to include items with AD, AP, and/or AS. One thing you could consider is a Guinsoo's Rageblade as it gives you 45 AP and 35AD and has a very nice passive that increases your AP by 6 and AS by 4% stacking up to 8 times. While I haven't tried this myself, it seems as though it would go well with this build. Not sure what I'd give up to get it though, possibly instead of a Wit's End or Malady.

Another item that might work, an item I use on a similar build with Teemo, would be a Nashor's Tooth as it provides you with AP and AS. While the passive of 25% cool down reduction is nice, Kog' Maw has pretty low cool downs and this reduction might not be worth it. If I were to build it, I'd most likely replace Wit's End as it packs a little more attack speed.

Summary

This is actually my first time making a build and while I'm new to this, I hope it's at the very least something helpful. Any feedback, good or bad is appreciated and I will take all the helpful advice I can get. I understand and appreciate the time and effort people put into these guides, this being my first one, I had now idea how much else there was apart from the initial build. I'll continue to update this build as I go along and I thank you for checking it out. I play a lot of Kog' Maw, not just with this build, this is just my preferred build. I encourage you to pick up this champ if you don't already have him, he's a lot of fun to use and my favorite in this game.