This is my first build, so please do not flame. Any feedback is appreciated!

Most of the inspiration from this build came from here: http://www.mobafire.com/league-of-legends/build/crabgot-the-crabpeoples-pride-67894

The goal of this build, is to harass your enemies. Not really to get kills or farm, but this provides a safe and effective way to demolish your enemies, while maintaining health and mana.

Pros:

Great solo damage
Incredible range!
Superb ability to kite and chase

Cons:

Slow
Extremely difficult to take on more than 1 person alone. Even if running
Susceptible to ganks.

I use the runes that are above for a few reasons, first off is that urgot really only needs runes early game. Late game he will be built so that all his runes are rather useless.

I have mana regen runes because early game he is extremely mana heavy, and can sometimes be defeated due to that.
Armor pen because all of his skills/attacks are physical damage. Seriously. Every one of them.
And CD reduction runes because his skills are rather high damage, being able to spam them makes urgot even more win ;)

Flash- Supplies a much needed escape method, as well as a chance to tower dive a foe.(Highly advised against) This also gives you the ability to go through a thin wall in the event of a runner (like master yi) who is trying to escape by pure speed.

Ghost- Also a very needed escape. Since you have no speed buffs other than your mastery's 3% and your boots level 2, you need a chance to run. Urgot is extremely vulnerable if outnumbered. However in a even match he can destroy, focusing two targets just does not work!

The biggest thing about this build that may make you go "Whoa wtf? Is he crazy?" Is the vampiric scepter building into wriggles. There are several reasons that I have included these items.
A: Urgot has very little regen compared to most chars, and as this build has no HP regen items, vamp seriously helps
B: As Urgot, you don't wanna waste all of your mana on minions, with the 500 damage chance, it makes farming much easier.
C: The ward is an incredible advantage if you are playing mid. As it can give you warnings of possible ganks, and can be used to counter a jungler early-late game.

The rest of the build is pretty obvious, stack AD and mana while stacking armor at same time.

The last 3 items are purely circumstantial. If the enemy has a high HP tank, get the black cleaver, if they have fast chars or you are getting focused, get the frozen mallet, if you need that extra vamp or regen, get Bloodthirster.

I start with Acid Hunter purely because it has massive range, and a quick recharge. It is easy to harass someone who is sitting at a tower typing away or just looking at a ally. Just sit out of range and start shooting. Eventually they will get smart and run out of your range.. After that you just stack acid hunter and Noxian Corrosive Charge to long-range murder your enemies.

This build is designed to maximize lane time, while maximizing harassing ability. This build it is extremely easy to get a early-mid game kill spree from middle. You dont want to start doing too good as eventually you will begin being ganked and focused, however this is where your Wriggles can come in. If you have bought it, place it on the side most likely to get ganked from to try to anticipate a move. Basically, use Noxian Acid, Use Acid hunter, use shield to slow, and run the hell away. Your goal with this build is to harass, at no point should you ever be tower diving until maybe very late game when you have your shield at max level.

While Urgot is a very good middle character, he can also be a great farmer. Urgot has two things going for him when he farms, the first of which, is obviously his area of effect from Noxian Corrosive Acid. This skill alone can take out a entire back line of caster creeps with one cast. Late-game, if you cast it into a large group of creeps, you will need to hit all of them at least once in order for the poison to completely kill them.