I know what you guys are going to say "oh thats a stupid build". But before just looking at it and downvote, try it out. I reckon you guys have never seen a dps cho'gath before, but here it is. I give credit to XxDimSimxX for this build as we made it up together.
And this is my first build so dont be mean. And by the way, when you get your whole build and have enough for a phantom dancer, i recommend you get it (switch with the boots).

PROS

-Super damage late game
-Fair bit of hp with your max stats of feast
-Squishy Pwnage
-Almost unstoppable late game
-Hard to kill with all your lifesteal items.

CONS

-Targetted often
-Gets owned if you get CCs in ur @ss
-Almost useless (damage-wise) until lvl 6 when you can ks >:)
-Easily ganked with no escape skills (rupture doesnt count as you have to GET the hit for it to affect them and if you miss, you're practically screwed :P )

I chose 21/0/9 as because 21 for all your damage needs and the 9 so u can stay in lane longer and also for the death time reduction(no one likes to be dead).

RECOMMENDED

EXHAUST - I LOVE THIS SKILL! I always get it for about every champion (other than casters) Good for chasing or killing those annoying dps carries.

IGNITE - this skill is usually to ensure your kill and for this build, you need all the kills you can get. Its also to half the heal and get the kill easier.

OPTIONAL

GHOST - This is pretty good for those chases or running away, you could switch it with ignite but exhaust is a MUST.

FLASH - This skill is the king/queen (whatever you prefer lol) of all escape skills. Good for "teleporting" through unpassable terrain or getting last hit when people are running away.

NO-NO'S

these are the useless summoner skills

CLARITY - Why do you need this? Its useless. This is a dps build so you dont need to spam your skills.

9 Armor penetration marks so you can do more dmg obviously
9 Critical damage seals for the extra damage you will be doing mid/late game
9 Critical chance glyphs for those "lucky" crits early game which might even get you a kill!
3 Critical damage quintessences for the extra damage for mid/late game

VORPAL SPIKES

As a dps build you have to max vorpal spikes first. It is very useful as it helps you deal more damage later on in the game. At late game when I got most of my items, I was killing squishies in 3 hits.

FERAL SCREAM

This is to silence those pesky little mages (casters) to make them practically useless or to get those last hits.

RUPTURE

I use this too hit those dps carries (such as Master Yi and Xin Zhao) up and get to killing them in mid-air. Its also good to hit people running away or chasing you. A very useful escape/kill tool.

FEAST

THIS HAS GOT TO BE ONE OF THE BEST ULTIMATES/KSING TOOLS IN THE GAME! Low hp people = instant death around cho'gath. Think of it like garen's ultimate but you gotta get into attack range. I'm a shifty one. I just run in and ks my teammates xD with this skill. .

I hope you liked this build (I couldnt add skill pictures because this is my first time > <") Hope you try it and love it. Don't downvote without commenting. Thanx for reading guys/girls!
Gl and Hf, hope you "pwn" :). With this build, after getting to lvl 18 (which you all must have already) and getting your full build. You will be able to solo baron.