This is how I play Cho'Gath . It is certainly not the end-all be-all for how to play, but I find it maximizes many of Cho's capabilities better than a tank build or an AP-heavy build.
Cho'Gath, The Terror Of The Void, was the first champ I ever bought (along with Morgana, The Fallen Angel). He looked cool, he had sustain, and the best damn skin in the game. So I looked up builds, and guides, and played with him... and I sucked.
I fed like hell, my cs was ****py, and even for a noob I was bad. Sure I could clear a min wave, and do a tonne of damage with QWR combo. Then what? Run away, and wait for the cooldowns to be over?
So I ditched him, and claimed he was UP, and instead played Morg and MUNDO. When I bought Orianna, and played around with AS/AP Ori (she sucked too), I decided to try it Cho. The rest is history.

Tank Cho'Gath does an amazing job of debuffing the other team, but doesn't bring much other than being a big target and providing auras. Also, his long cooldowns leave much to be desired after the initial burst.

AP Cho'Gath has the same problem, but worse. AP Cho is harder to stay alive with, as Feral Scream, Vorpal Spikes and especially Feast are all close range. Cho tends to be a bit squishy without stacks on his Feast.

Tanky/DPS/AP Cho does better than any other I've seen so far. And that ain't much, cause few people play Cho.

9 Greater Mark of Magic Penetration

9 Greater Seal of Armor

9 Greater Glyph of Scaling Magic Resist

3 Greater Quintessence of Magic Penetration

Mpen is one of the hardest stats to buy. The marks and Quints will give Cho 15 Mpen, without losing out on the fantastic tanky qualities of various boots. Since most of his damage is magic, and this build runs several magic damage-dealing items, these runes are *vital*.

The armor and mr/lvl runes are pretty standard for tanky dps champs.

Boots and pots to start always. Cho needs the sustain and mobility because Cho is very weak this early; Cho is technically a mage, and scales with levels.

Don't poke with anything other than your Q yet, you'll lose skirmishes.

Fiendish Codex > Nashor's Tooth Gives Cho everything he needs early: mana regen, CDR, AP, and then AS.

Once you're level 5, and you can trade well, you should be pushing your lane *when bot is not mia* and doing the smaller camps in jungle. Only do the big camps once you're level 8 and have your Feast ready. And ward red buff, you'll have the CS to be able to spend 75g.

When turret tapping *securely (no enemies near enough to stop you), position yourself so you can kill minions while attacking the tower, or walk past it and kill the minions as they come. Until you have a fair bit of AS and AD, tapping will be more effective if you let your minions do it without interruption.

In teamfights, Q the carry (or the main threat if the carry isn't) silence as many as possible *unless one of them has a channeling ult. Then save it for when they try it eg. Absolute Zero Death Lotus Nether Grasp ect.*

Feast the squishy ASAP. Doesn't matter if you don't have max stacks on your Feast, only save your Feast if it's a 1v1 fight. If it doesn't kill them, it'll scare them maybe enough to start to run. then Q, and E to death. It also signals to your team who you're targeting (and who they should be).

If positioned correctly, Cho's Vorpal Spikes can damage the whole enemy team, and even minions to allow for some slight sustain from Cho's Carnivore (although this is better used in 1v1 situations).

If the enemy team is far *and you're sure of this* then after getting Nashor's Tooth, Cho can solo Ebonmaw. Use health pots if you have them, and let your team know you're doing this and they should be ready to assist you.

Clear camps, try to get all the buffs (they all work so well with Cho). This also prevents the other team from claiming them. If the other team is killing Ebonmaw, you can always steal with Cho's Feast.

Feast> Vorpal Spikes> Feral Scream> Rupture

Feast You eat them. It does amazing base damage, good AP scaling, TRUE DAMAGE, adds health to you when you use it as a killing blow
Vorpal Spikes is the main damage skill of this build. It causes Area of Effect damage in front of you (and a bit to your sides). It adds a fair amount of damage, much like Dr. Mundo's Blunt Force Trauma, but for free with no cooldown. It lets Cho trade early, rather than just bursting (and likely missing) his Rupture. The damage will get better as AP and Mpen, and AS is added. Allows you to farm, trade, and farm while trading (which will heal you slightly due to Carnivore.

Feral Scream is a good source of early game damage and (occasional) harassment, and scales to a three-second AoE silence. When at level 5 with some AP, it can clear min waves alone. However, it has a rather high mana cost, and a long cooldown, so it's best not to spam it, especially in teamfights with channeling champs.

Rupture Fantastic base damage, 1:1 AP ratio, and a knock up and slow. It's vital for ganking as Cho, and if you can aim it properly more often then not, I HIGHLY recommend maxing this before Feral Scream. On the downside, the actual CC of the move does not scale with levels.

Mercury's Treads Do they have hard CC? (stun, fear, taunt, ect.)

Ninja Tabi Do they have more than one auto attacker? (Vayne, Yi, Ashe, ect.)

Boots of Swiftness Are they well balanced?

Sorcerer's Shoes Feeling saucy?

Nashor's Tooth CDR on Cho is a must. His spells have long cooldowns, and his ult needs to be spammed whenever he has less than max stacks. 25% CDR this soon will let you keep your stacks up, use your CC when you need it, and spend more time devouring things. The mana regen truly helps what little mana sustain Cho had, the AP gives him a nice boost, the AS lets him trade, farm, jungle ect. And each upgrade costs very little, so you can buy any bit you can afford whenever you return to base. Get pushed out of lane? Now you have more AP or mana regen or CDR or AS.

Madred's Bloodrazor Adds slight armor, AD, AS, and a fantastic magic damage proc. Rips any enemy apart very quickly, especially jungle camps. The additional AD it gives lets Cho kill towers much quicker. Best of all, if they stack MR, you can build more AD items, and if you stack armor, you can build more magic damage or AP. This item has fantastic synergy for both.

Abyssal Mask Removes MR from opponents(!), adds AP and MR. AP adds to Cho's auto-attack damage through Vorpal Spikes, as well as all his other spells, which have great AP ratios. Also, Cho is a close range champ, so the entire enemy team will be debuffed by this aura.

Rabadon's Deathcap Adds a metric ****tonne of burst to all of your spells and auto-attacks. This is best late game where burst damage may decide who gets the ace.

"Only 5 itmes?!" Read the next section, and figure out what you need from those. Cho is one of the most adaptable champs, USE THIS.

Is their team not balanced? Take advantage!

Wit's End Adds AS, more magic damage(!), and MR/hit. A great counter to magic damage if you can close the distance, a good one even if you can't. Also counters Madred's Bloodrazor effectively. The best versus AP/hybrid melee champs (eg. Warwick, Mordekaiser, Evelynn, ect.) A solid choice.

Hexdrinker / Maw of Malmortius Only if you already have Abyssal Mask and Witt's End]] already. It doesn't provide a whole lot of damage or tankiness for the cost, but this is still better than a full tank item like Force of Nature. If you're getting this, substitute Rabadon's Deathcap with a Bloodthirster.

Glacial Shroud / Frozen Heart More mana, more armor, more CDR (max at this point). These counter auto-attackers pretty effectively, especially because you're in their face. This is the only tank item I'll suggest, because it's such a good fit as a counter.

Atma's Impaler and/or Sunfire Aegis Both are good counters to non-auto-attacking AD champs.
Atma's Impaler Adds raw AD, armor, and a rather pointless crit chance. Works well with Cho's Feast stacks and any other health bonuses, like...
Sunfire Aegis Adds magic damage(!), raw health and armor. Since you're in their face anyway, this will add to the AoE damage you cause. It's an especially good counter to Olaf.

Thornmail Only get this if a auto-attacking carry is dominating. It adds armor, and deals magic damage(!). This is good because if you have your Abyssal Mask and full Mpen runes (and Sorcerer's Shoes, if you're saucy) you may just do more than 33% back. *However* this is bad because most champions don't use auto attacks as their main damage source, and this adds nothing at all to the build other than armor. Only get this as a counter to a fed Tryndamere, Master Yi ect.

Bloodthirster Why? Because if you already have a few AD items (eg. Maw of Malmortius, Atma's Impaler, Madred's Bloodrazor) and a few AS items (eg. Madred's Bloodrazor, Nashor's Tooth, Wit's End) then this will let you really hit hard. The main reason this is viable at all is that Cho'Gath is fantastically good at killing creeps, perhaps the best in the game. This will reach max stacks very quickly and won't be hard to restack after dying. The sustain works very well with Maw of Malmortius, as you can hover at low health quite easily. The main problem with this item is, as with losing Feast stacks, you can snowball backwards with deaths. Don't be reckless with this item.

Any pure tank items (eg. Force of Nature, Warmog's Armor), burst items ( Zhonya's Hourglass, Deathfire Grasp), positive auras ( Soul Shroud, Zeke's Herald) or pure AD carry items ( Phantom Dancer, Black Cleaver, Infinity Edge) while good items, are not for this build.

Gp/5 items (eg. Heart of Gold, Philosopher's Stone, Avarice Blade, and Kage's Lucky Pick) as much as I love gp/5 items (and I really do) they do not build into anything useful for this build. With your knock-up Q, your AOE three-second silence, AoE damage, and negative auras ( Abyssal Mask and Frozen Heart), you have already given your team enough to work with. You do not need support-build auras and actives.

Malady Sure it adds AP and AS, but not a whole lot. Sure it's proc is good, but only for early game when you won't be in range most of the time. It works for Teemo because he's ranged, and has a speed boost. Cho won't be able to make the most of it, and other items are better anyway. On Cho, it slows down his great items, and takes up a slot in late game.

Hextech Revolver / Rylai's Crystal Scepter Or anything that builds out of Hextech Revolver. The slow is reduced for AoE damage. And you already have a slow. Spell vamp on Cho is bad for the same reason. And you already have sustain.

Guinsoo's Rageblade Seems like a perfect fit. But it adds nothing but damage, no CDR, no armor, no MR. While it looks good, no item is worth losing in place of this. If you want flat damage so badly, rush Rabadon's Deathcap and/or Bloodthirster. But then it's a carry build, and this is a tanky/DPS/AP build.

Trinity Force Another seemingly good item, but no. Everything it does that gives synergy to the build, does it in small amounts. There's just too much wasted potential.

Lich Bane All of Cho's cooldowns are long. There are better items.

Flash Good ol' Flash'n'Feast. Also, Twisted Treeline is full of great places to flash over, take full advantage.

Exhaust or Ignite Whichever your team needs. Always be sure there is one of each in case of Dr. Mundo, Swain or Fiddlesticks, or any given AD carry.

Ghost To let you run across the map to a teamfight some idiot started, to steal Ebonmaw with a Flash'n'Feast, to suicide on their Pool Turret just as the game ends in sweet victory.

If you don't like using certain items, then play around with it. If you find something cool that works, lemme know. If you think an item that I said I don't like works, give me a proper, logical reason, and I'll respond. I'm open to all constructive criticism.

Try the build, see if you like it before voting.

And for gods' sake, get a damn skin, they're all good.