Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
First off this is my first attempt at a build so if it's bad let me know so i can fix it.
This is a hybrid Kog'Maw build so obviously there is a mix of AS, some AD and a good amount of AP.
For masteries I use a somewhat common 21/0/9 set up. I skip 2 points in lethality to put them in alacrity, other than that its a standard offense. In utility I take haste mana/health regen extra xp and greed.
Note: other set ups I have used take 23/0/7 taking full lethality for no greed and one point out of awareness.
There are a few different spells that are useful with this build. I prefer Ghost and Flash, Ghost for chasing and running away, and flash for the same reasons, and the ability to flash through walls to set up mortars for enimies. Also viable are Exaust and Clarity. Exaust is good for some measure of survivability and perhaps damage although the range is low and somewhat counter productive, and Clarity is good if you find yourself low on mana too much for your liking.
My rune choices might seem a little odd, but I find that these runes fit a hybrid Kog'Maw well. AS is a mainstay for his physical DPS,AP and Magic pen give his spells a bit more force behind them. The mana regen seals are helpful in keeping more of your mana there during fights and help lessen the downtime of your casts.
Items, one of the bigest things to look for in a build. I start out with a Dagger to get some AS then when I can upgrade it to Zerkers boots. Imidiatly after this I start to work on Sheen, usualy buying the tome first if I can't buy it outright. that leads me to a Bloodrazor, one of the must have items, wicked on hit when stacked with BAB and CS. A phage comes next for a little more health and the slow, this along with the sheen should be upgraded to a Trinity Force at some point. Next comes a Rageblade, another of the items that makes this build viable. Nashors' Tooth makes an apearance in this build as well, but the placement of it in the buy order can be tweaked for personal preferance, I usualy get it right before my Black Cleaver and after my Bloodrazor. The final item I grab is a Black Cleaver. This is not compleatly necessary, but the stacking armor reduction on top of what your CS has cripples even the most armored out tank, and once again AS is one of your best friends.
This build has an emphasis on your BAB, that being said I think that your first point should go into CS. CS gives a little more farming ability in the first bit of play and level 2 is reached so easily it hardly matters. After the initial two points I try to max CS and BAB as fast as I can, while taking my ult when I can and Void Ooze at 4, 8, 15, 17, and 18.
When in a fight hit your target with CS as fast as possible, then back out and pop BAB. If they run slow their *** down with a VO and pound away. Very few champs can survive this combo for long.
You WILL die with this build, it lacks survivability and you put out massive damage so you will be tunneled down in a team fight. Make your passive count for something, and make the *****es that kill you pay.
This build is by no means the best Kog'Maw build, but I find it the most fun way to play for me. It is efective and somewhat hard hitting while capitilising on Kog'Maw's versatile damage dealing abilities. You can hit just about anyone hard, and it leaves the other team confused because you can sit and spit at them and they die, or you can log green stuff at them, and they still die, stacking armor or stacking Magic resist leaves a hole for you to exploit, play with items and see what fits best in a certain situation.