I like playing Cho'gath so I wanted to try and think of a different and unexpected way to play him. I was buying Nashor's Tooth and liking how the attack speed worked. Then I though that with his vorpal spikes, an attack speed build could be pretty sweet. I'm only lvl 20 so I haven't seen what full masteries and full runes can do yet.
I'm sure there's more to be said and as I discover things about the build I'll try to post and talk about them.

Runes are the normal fair. The armor helps him in melee and the magic pen and ability power make his abilities stronger. You may want to consider replacing the ability power runes with attack speed runes.

For the items I like to get Rod of Ages early so it can hit full stacks sooner. The boots are great and when combined with phantom dancer and quints it is very hard for someone to outrun me or to catch me. After that I'd just leave it up to you to decide what you want. Should probably go for the Void Staff if the other team is building a lot of magic resist. Alternatively you could just build another Phantom Dancer.

The obvious pro is damage output. Even if your opponents build a lot of magic resist you'll still be doing damage against them and you can build a void staff to counteract it. By using your pop up you can surprise them or just give you that extra slow to catch up. If you're far enough along in your build they probably can't get away with your speed and your silence keeps them from trying to escape with an ability or spell while doing a nice bit of damage itself. The good constant damage output leaves them open for Feast too. Last hitting minions is very easy with the wide spread of the spikes.
Cons are that you're not building any magic resist or armor so you'll want to get your feast stacks up as quick as you can, preferably by using it on siege minions or monsters in the jungle.

Your speed can help you initiate and escape from jungle encounters as well as let you kill monsters quickly.

Ambushes are the best after the enemy's been softened up and have possibly already blown cds to escape meaning they won't be able to escape you.