First of all, I'm sorry for my bad english and hope you don't have problems to understand this guide.
I'm writing my first guide to show you my variety of playing Urgot. This guide should only show an opportunity. You should also look into other guides to complete your ideas and knowledge about this champion and how to play him.
Also I'm sorry for my wall of text.

LINK TO OTHER URGOT GUIDES!

This is a guide for playing Urgot as a tanky solo top champion and NOT as a ranged carry.
But with this guide you will also use big potential of Urgot's skills and damage output in early game and probably more use of his ultimate.
I hope this guide (maybe) help you. Also please give me a feedback, what you would like to have in the guide included or things you would like to change (maybe items, runes, etc.).

So...why playing Urgot if I can also pick other champs?

+ for playing Urgot

• he has a VERY strong early game
• very good harassment
• very good passive -> Zaun-Touched Bolt Augmenter
• extremely strong in 1 vs 1
• (in my opinion) very funny ultimate -> Hyper-Kinetic Position Reverser
• can definately change a teamfight/ game if spells are set well
• big range ( Noxian Corrosive Charge + Acid Hunter) also normal ranged attacks
• he has a shield -> Terror Capacitor
• good spells to explore bushes -> Acid Hunter and Noxian Corrosive Charge
• I love his crabby skin :D

- against playing Urgot:

• you need mana giving items or mana regeneration items to harass well
• you need to know where enemies are, also if you dont see them (landing Acid Hunter after hit an enemy with Noxian Corrosive Charge)
• positioning is important
• only 1 AoE -> Noxian Corrosive Charge
• not very good in dealing dmg in 2 vs 1 or bigger fights (against all)

Urgot is a very good bot lane champ so why playing him top?

• Well, playing him solo top allows you to have a 1 vs 1. This gives you the chance to harass only 1 enemy, who can't heal himself (normally). In cause of this, the enemy is forced to play defensive (he won't get that many last hits than before) or to port back, so the jungler may come top. -> won't be an enemy gank (probably); your jungler can farm in enemy jungle.
  
• Also you're a ranged champion against many melee champions. You will have more space to attack and easier farming than the enemy and you don't get much damage from the enemy.
  
• Urgot's ultimate is very usefull and can change a teamfight if set well. But you'll be ported into enemy team after casting it (teamfight) or ported near a tower. So you need to be tanky so you can get much damage without dieing.
  
• Urgot has a extremely good early game. But his damage is going down from time to time. His Late game is not the worst, but also not the best.

-> Playing him tanky with some damage items allows you to deal good damage in early/mid game and be tanky enough to cast your ultimate without caring about your position after.

Passive: Zaun-Touched Bolt Augmenter -
Urgot's basic attacks reduce his targets' damage by 15% for 2.5 seconds.

Note: This is an extremely good passive. If you hit an enemy, he is doing less damage. Changing teamfights is easy with this passive!

Q-Skill: Acid Hunter -
Urgot fires an Acid Hunter missile that collides with the first enemy it hits,dealing 10/40/70/100/130 (+0.85) physical damage and slowing the target if he has his Terror Capacitor up. Acid Hunter missile-locks on enemies affected by Noxian Corrosive Charge.

Note: This is Urgot's main skill. The cooldowns are low and the damage is very good in early/mid game.

W-Skill: Terror Capacitor -
Urgot charges up his terror capacitor to gain a shield that absorbs 80/140/200/260/320 (+0.8) damage for 7 seconds. While the shield is active, Urgot's attacks and missiles slow targets by 20/25/30/35/40%.

Note: A very good shield, slowing enemies if you hit them. Very usefull while chasing or getting chased. Also good if casting Hyper-Kinetic Position Reverser into the enemy team.

E-Skill: Noxian Corrosive Charge -
Urgot launches a Corrosive Charge at a target location. Enemies afflicted by the charge have their armor reduced by 12/14/16/18/20% and take 75/130/185/240/295 (+0.6) physical damage over 5 seconds.
Acid Hunter is able to missile-lock onto targets affected by Noxian Corrosive Charge.

Note: Nice skill, reducing enemy armor and automatically hit with your Q if mouse is hold over your target. If you hit multiple enemies in a teamfight, it's also changing the teamfight.

R-Skill: Hyper-Kinetic Position Reverser -
Urgot targets an enemy champion and channels his Hyper-Kinetic Position Reverser for 1 second, swapping locations with his target afterward. His target is suppressed for the duration of the channel.
Urgot gains 80/105/130 armor and magic resist during and after the channel, and his target is slowed by 40% for 3 seconds after being swapped.

Note: Really good ultimate if you want to pick out an enemy champion out of his team.

Coming in the next days.
Sorry.

Good choices as summoner spells for Urgot:

Flash: Teleporting your Champion instantly to a nearby location under your mouse cursor. (Not over the whole screen)
-> One of the most usefull spells in LoL. This spell allows you to escape ganks, chase or warp over a wall. Very usefull for Urgot e.g. after using ultimate to warp back to your original position.

Teleport: After a short casting time, you'll teleport your champion to an allied minion or turret.
-> Very usefull for ganks on other lanes or teleporting to a tower or your lane after backporting.

Exhaust: Slowing movement speed, basic attack damage and ability/item damage for a short duration.
-> This spell can often save your life or help you to get a kill. Using it in addition to your ultimate or your shield slow could be a very strong combination.

Possible choices as summoner spells for Urgot:

Ghost: Allows you to walk through units and faster movement speed.
-> This spell allows you to run after an enemy champion or away from them, if you are getting chased by them.

Clarity: Gives you and your allies around you mana depending on your level.
-> This spell is helpfull, if you can't manage your mana, but you should gradually learn to play without it (tip of my hand).

Heal: This spell gives you and your teammates around you some health back depending on your level.
-> Also a helpfull skill, if you're on a summoner level or to to change the teamfight with healing your team. But like clarity, you should gradually learn to play without this spell, because there are some better spells.

Ignite: Targets an enemy champion and dealing true damage over 5 seconds. Also reducing healing and regeneration of the target.
-> Often a deadly skill. And in addition to your E-Skill a more deadly combination of 2 damage over time skills. But you don't need to get many kills in teamfights, 'cause you're going to be a tanky damage dealer, getting more assist than kills, so your Carry or Mage can get the kills.

Cleanse: This spell removes all disables and summoner debuffs from your champion. Also lowers the duration of incoming debuffs by 65% for the next seconds.
-> If you jump with your ultimate in the enemy team, this spell can help you not to be immediatly cc'ed for the rest of the teamfight (if you're unlucky and get focused with ccs). Also you can use skills to help your team.

Bad choices as summoner spells for Urgot:

Surge: Surge gives you a bonus attackspeed and ability power for a while.
-> Urgot gets his most damage out of his skills, so your auto attacks don't have to be very fast. Also ability power is useless on Urgot except for the shield.

Smite: Dealing much true damage on minions or monster (NOT champions).
-> This spell is usefull for the jungler. Not for you.

Clairvoyance: Using this spell reveals an area of the map for a short time.
-> This spell is for the supporter. Leave it for him/her to pick.

Promote: Promote will change the nearest siege minion (or ) to an anti-Turret Cannon. The minion will be healed, gets bonus stats and you'll get the gold of the minions, the minion kills.
-> This spell is usefull for pushing lanes. Not for more. You can push, if the enemy is going back or plays very defensive after your harassment. So you don't have to pick that spell.

Revive: This spell revives you after your death (you'll be at the Summoner Platform, NOT on the point you died) also giving you maximum health and bonus speed (if Summoner's Resolve is skilled).
-> Never ever pick that spell! You can use that spell every 9 minutes!!! Picking that spell also means that you'll die (~ every 9 minutes to use the full potential). And you don't want to die. In the best case not a single time. So don't pick it.

Marks:
I prefer 9x Greater Mark of Desolation. You'll get 15 Armor Penetration which allows you to make more damage. Mainly in early game, 15 Armor Pen can be very much.

You can use other Marks, but these are actually the best Marks for Urgot.

Seal:
I use 9x Greater Seal of Armor, which give you 13 armor to stay longer against AD-Champions, minions and monsters.
You can also pick Greater Seal of Replenishment or pick Greater Seal of Scaling Mana Regeneration if you can't manage with your mana.

Glyphs:
Using 9x Greater Glyph of Magic Resist allows you to stay longer against Ap champs.
Alternetives are Greater Glyph of Cooldown Reduction(if you pick them, remember that you always have 39% cooldown reduction in late game, so many of these runes aren't very usefull) or Greater Glyph of Scaling Magic Resist.

Quints:
Using 3x Greater Quintessence of Desolation give you a total amount of 25 Armor Penetration in early game, which allows you to deal true damage to nearly all Champs in early game.

I start with a Meki Pendant and 1 Health Potion and 1 Mana Potion. This allows me to stay very long at the lane, harassment of enemies and the Meki Pendant can later be changed into a Manamune.
You can start with Boots, too. Or you buy instead of potions a ward. But this is up to you.
After first time going back, you should have at least Boots or Meki Pendant(if you started with Boots of Speed). Normally, because of having a very good endurance, you can also buy a Tear of the Goddess which gives you the ability to gain extra Mana while spamming your spells. Otherwise you can buy wards or potions(if needed).

Next time going back you should buy better boots (e.g. Mercury's Treads).
I prefer Mercury's, because getting stunned may take too much time, so you may can't use your ultimate or Flash,.... . BUT think about the enemies! If they have 4 AD champs(rarely), you should buy Ninja Tabis. So adjust the Boots to the enemies.

Next times going back you should be able to buy The Brutalizer, Glacial Shroud and Manamune (maybe 2-3 times going back). Manamune is very good at Urgot, 'cause you get Mana, Mana regeneration, Damage, and extra damage for your mana. Isn't it nice?
The Brutalizer and Glacial Shroud are very helpfull items. You get 20% cooldown reduction (total), damage and armor penetration(from The Brutalizer) and armor and mana from Glacial Shroud. The extra mana also give you bonus damage, 'cause of Manamune.

Last item is Frozen Heart, which you can build out of Glacial Shroud. Frozen Heart gives you much armor, more mana, and more cooldown reduction. With these items you have a total cooldown reduction of 39%, so only 1% under the maximum limit.
This is the CORE-BUILD (imo).
With this build, you're able to deal decent damage, while being tanky.

The last two items aren't always the same. If the enemies have many ADs or a fed AD, Randuin's Omen, Sunfire Aegis, Thornmail and an Atmas Impaler (if you also buy health items) are good choices.
Against a team with many AP champions you should buy a Force of Nature or a Banshee's Veil.
Against mixed teams you can buy one item of each cases (Against AD team or AP team) or you buy a Guardian Angel.

But I would take some magic resistance, because you always have ~100 bonus armor and only ~35 magic resistance. Also pick some health items you like, so you can survive teamfights. Good choices could be: Sunfire Aegis, Warmog's Armor or a Randuin's Omen.