Not Updated For Current Season
This is a AD/AS Kogmaw build. I enjoy playing Kogmaw the most of all characters in this game. I have tried many different builds with Kogmaw and this one takes the cake. It destroys tanks in seconds and pretty much decimates everything else. You will see critical hits for between 600-800 in late game play with an attack speed of over 2.4. Along with using Bio-Arcane Barrage with Madred's Bloodrazor doing 11% of the enemies life every hit.
For runes I use all Attack Speed runes. It starts you off at the beginning of the game with around 38% increased attack speed. This will put you around just under 1.0 attack speed at the start of the game increasing your chance to get last hits on creeps.
I use Ghost and Flash because you need to have outs. Kogmaw does not have much of an out other than his Void Ooze which is minimal at best. I would not use anything other than these 2 summoner spells for the escape mechanics alone to just survive.
Early Game: I start out the game with Vamp Septer because it allows you to maintain in the lane for much longer than going a Dagger and health pot. The goal is to be able to stay in lane until you have enough to get Boots and Zeal (2115 Gold for both) or if you end up needing to go back get Boots first.
Mid Game: By now you should have at least Madred's Bloodrazor and also be cloose to getting your Phantom Dancer. Once you have these 2 items your damage begins to get much better.
Now just follow my build order up top for the rest of the game. The reason I got with Hextech vs Bloodthirster is Hextech will give you enough AP to boost your Bio-Arcane Barrage to do another 1% additional damage per hit and the spell vamp and Life steal are amazing later in the game.
Pros / Cons
Skill shot can take out runners
Takes a bit to master
Focused all the time
When playing this build of Kogmaw I have to play very cautious the entire game. Wait for the opportune time to go into the fight once people are engaged and watch them melt. When you use your Living Artillery use it very cautiously because you will fry your mana very quickly. Use Living Artillery to scout bushes and pick off runners with low health. Do not use it as your main damage. You need to save your mana for Bio-Arcane Barrage(which is your main damage dealer) and Void Ooze(to escape or slow enemies).