So I love Kog'Maw, however I do not consider myself the best player nor a pro or any such title, I do however enjoy a few of them very much. I dont know if there is a similar build out there but I have done very well with this one, this is also my first build guide so I will probably have to update it as I go along, please let me know what you think and what could make this better, I am all about improving my game. OK so here goes.

The first 5 Items I would leave exactly how they are, although I would buy first level boots and 3 health pots to start, finish boots, then follow the list as it is presented. Infinities Edge is only there because I like to have some end game attack damage, however you could replace that with a frozen mallet, or another blood thirster, or any number of items depending on how your game is going.

I will say this about my guide, your W attack is your bread and butter, everything else is just there for flavor. After you get your madreds your be doing 10% of their max health every time you hit while W is active, not to mention if they start to run you can void ooze (E) to slow them and slap them with your ult to finish them off. whenever you engage an enemy hit them with your Q ability first to reduce their armor and do a bit of damage, then pop your W and go ahead and slap E and R abilities on them as well and let the W take its course, you should be able to take on 2 or 3 people at once when you have your lifesteal going and your madreds on you. Also remember you have one of the furthest ranges in the game, and its that way for 3 of your abilities (Q ability is a little short range comparatively).

Mid to end game you will be the best pusher/tank killer/Carry destroyer/turret muncher on your team, unlike other champs I would focus on tanks or any champion that may have been fed early game or just being a nuisance. Eventually their team will start to focus on you in fights, this build does not give any survivability with the exception of your flash (or any 6th slot item you decide to buy that does give survivability), while it is active. So I suggest playing smart and using your range to your advantage. This build gives you a good base for any job within your team besides taking damage, so kill them before they get to you and work with your team, you are an essential part of team fights, and never forget once they kill you you have a few seconds to run them down and blow them up, you will get a revenge kill immediately to any gankers, or you can rush into a group of them and bring their health down for your team to finish them off, giving you a few assists, which aren't bad either.

Also remember that you not only can destroy other characters with your W, but you can soften them up with the best harass ability in the game, Your ult. It has almost no cool down and does a butt load of damage, not to mention it marks them for a few seconds after being hit, and is an area effect.

Farm lots and often, try to get a Mid spot to get the farm up and rush your maladys after the boots. late game you can wade through minions and just rake in the money. You also will use them as your primary health restore during the course of the entire game, constantly kill minions to gain health after taking on enemy champions.