To the solo top guide for Pantheon, the Artisan of War!
In this guide, you will find out how to exactly go use Pantheon to your advantage to carry your team to victory.
This build will also concentrate on his ability to survive in fights, and also to dish out tons of damage to your enemy team.

Pros
-Lots of Damage
-Scales amazingly well with AD
-Has a stun
-Can 1v1 most melee champs
-Ult does TONS of damage
-Has high sustain if done correctly
-Destroys other squishies
-Fairly low cooldowns

Cons
-Naturally squishy
-Will definitely die if focused right away
-No escape skill, and depends on Ghost or Flash to get him out of battles
-Sustain is conditional (on-hit lifesteal)
-Timing his ultimate is a pain
-Landing it is even harder
-Counter melees may destroy you before you get to them
-Mana problems

I take Greater Mark of Attack Speed. This is to act in synergy with his passive, Aegis Protection. It also is to buff up his DPS amount. He doesn't really have that high attack speed, and your item build gives you no benefit for that, unless you take a Trinity Force. However, this is not the case.
Some optional substitutes are:
greater mark of desolation
Greater Mark of Scaling Attack Damage
Greater Mark of Attack Damage

For seals, I take Greater Seal of Scaling Mana Regeneration, in order to solve his mana problems. This benefits him in many ways: While he still won't be spamming his abilities non-stop, this will deny him the tendency to run out of mana.
If mana regen is not an issue for you, here are some viable options for you:
greater seal of defense
Greater Seal of Armor
Greater Seal of Gold in order to gain some gold since you won't have any gp/5 items.

Glyphs were a tough choice for me, but I ended up choosing Greater Glyph of Scaling Magic Resist, for the sole purpose of countering (somewhat) the bursty-ness of AP carries. I found I was having a hard time surviving against AP champs, and wasn't able to burst them down myself quick enough, or they would kill me before I would reach them.
Other options (though not recommended) are:
Greater Glyph of Magic Resist
Greater Glyph of Scaling Cooldown Reduction
Greater Glyph of Cooldown Reduction

Greater Quintessence of Movement Speed are pretty necessary. Pantheon has no movement speed boost, save for his Ghost if he has one. He gains no speed buffs from any items, and this is necessary if he is to chase down enemy players.
However, if you want to substitute them, I recommend:
greater quintessence of desolation
Greater Quintessence of Attack Speed
Greater Quintessence of Scaling Magic Resist if you still feel threatened by magic damage

I like to take Ghost and Ignite for solo top champions in general.
The reason why is because Pantheon already has a fairly high base movement, and is even higher with his boots, and with Greater Quintessence of Movement Speed. So when he goes back to shop, he can either run there, ghost his way there, or "teleport" by using Grand Skyfall.
I use Ignite to secure kills in early game when I'm in lane phase, and then to stop passives like Volibear's The Relentless Storm, or Dr. Mundo's ultimate, Maximum Dosage.

Other options?
Possibly:


If you need to get to the other side of the map faster than what your ultimate can provide.


Too much CC for your liking? Go ahead break out this bad boy.



I only take this if I know I'm going to be bursted down too quickly for my liking.


Use this if you already have enough ignites on your team. Simple enough.


Take this if you know you will have a difficult time pushing against your opponent.

NEVER TAKE THESE SPELLS.

Clairvoyance
Your support will have Clairvoyance already, don't worry about it.

Clarity
You already have seals for this. It also doesn't help you gain kills, chase, or anything of the sort. Just a bad spell for Pantheon in general.

Heal
Not worth it, really. The amount of damage you deal will act in as your own sustain because of how much lifesteal you will have. In my opinion, not worth it for Pantheon.

Revive
A worthless spell for Pantheon. Very unnecessary unless you are one of those who die alot no matter what the game is.

Smite
You don't jungle. You solo top. :]

21 in offense
This is to help sustain as well. 3% life steal will keep you in lane longer, along with the 3% from your Doran's Blade in beginning game.
And then Armor pen, flat damage, etc. to help you put out more, and establish your role more easily as a carry.
9 in defense
This is to add some sustain for you in lane. Health regen, plus flat MR and Armor will help you survive a bit longer.
0 in utility
Nothing in this tree of necessarily good interest.

Start off with a Doran's Blade. This gives you a nice damage boost, and will help you sustain longer with it's lifesteal.
On first trip back, take your boots, a longsword, and a couple pots or wards for more sustain, and to watch out for ganks.
Next trip you should be able finish off your phage. Afterwards you must build a Vampiric Scepter before you even think about buying that B. F. Sword. Why? Sustain in battle and in lane. This will up your survivability about tenfold once you get it. However, just because you get this item DOES NOT MEAN you are invincible. Pantheon's sustain is conditional only, so therefore, you must only go into a battle if you are guaranteed able to survive the fight.
Start working on your Frozen Mallet by buying a Giant's Belt and preparing for some synergy with Atma's Impaler in order to help you deal more damage, and to slow down enemies. This way you put out more on the enemy as they try to escape.
Next, we need some armor, so we go for a Chain Vest, and build it into an Atma's Impaler. This item will synergize with your Frozen Mallet that you buy next, and both will help you to survive team fights.
Finish of your Bloodthirster, and start stacking it up by pushing waves, or jungling etc. This will give you more damage, and more sustain with it's lifesteal.
In order to counter enemy armor, build a Pickaxe and finish off a Last Whisper. Pure damage item, with obvious reasons to buy.
Last, but most definitely not least, take your Infinity Edge. This is solely for damage purposes only. Buy a B. F. Sword before you finish this off.
But why save this item for last, instead of rushing it? Because you need to be able to survive before you are able to kill. You already have tons of damage output, plus you needed to be able to hold your own in team fights because you are a melee, and will be in the thick of things to boot. This item is solely for the sake of mass destruction once you enter a fight late game.

Skill order is based on harassment.
The Harasser
Spear Shot> Heartseeker Strike> Aegis of Zeonia
Take this approach if you have an opponent you know will be a problem to take on. Since you have Greater Seal of Scaling Mana Regeneration, you can throw your Spear Shot more often, and farm more efficiently with your Heartseeker Strike while your opponent backs off of you. Prioritize Spear Shot, then Heartseeker Strike, then Aegis of Zeonia in order to get maximum damage output.
The Roamer
Heartseeker Strike= Aegis of Zeonia> Spear Shot
Here, your opponent is weak against you, and you seek out more kills because you aren't satisfied. This skill order is meant to keep you able to farm, and push top, while allowing you to move in on ganks, stun them, and help finish them off with your Spear Shot, Prioritize your heatseeker strike and Spear Shot equally, and level your aegis once @level 3, maxing it out later.
The Farmer
Heartseeker Strike> Spear Shot= Aegis of Zeonia
This approach is aimed at getting your CS way way up. Take this path if your opponent isn't denying you farm, or your jungler is simply not concentrating on your lane. Prioritize Heartseeker Strike first, and level up your Spear Shot and Aegis of Zeonia at equal rates.

How to play a solid Pantheon.

In Lane:
Focus on harassing the enemy with your Spear Shot, and farming with your Heartseeker Strike. You should be fine as long as you're not too ballsy. Be sure to always have your passive up as much as you can, because it will save you from a lot of auto attack damage from characters like Tryndamere, Jarvan IV, Irelia, etc. However, you still need to dodge skillshots, because your passive does not block those -- only auto attacks.
If your enemy is gone from lane, push all the way to the tower, and be careful of ganks. Go back to base as necessary, or feel free to roam around to mid lane for a gank. When coming back to lane, and you don't have time to be behind, you can either use Ghost to get there faster, or Grand Skyfall if you fear you may lose the tower. Try to save these options if there is no imminent threat, howeverm because they will be necessary for team fights, and 1v1 battles.

Roaming:
Be sure that if you are going to roam, that your lane is clear, safe to leave, and there is no threat of a counter push when you are gone. Make sure you are at decent strength, and that if you gank you are guaranteed to push the enemy lane back, or will have a kill, and that you won't die.

Team Fights:
You will never be the first into a team fight. For one, you are too squishy. Two, you have no way out of a battle, only into one. And while you have high sustain with your life steal, this does not mean in any way that you are as brick-like as Alistar, or Jarvan IV, or Malphite. Try and enter the fight after your tank does, or there is a solid initiation from another teammate.. Try and stick with your tank, because he will also have enough CC to keep your enemies near you in order for you to snag some kills, and will also protect you from death.

When to Ultimate:
Before you even do so, make sure you are hidden well enough that no one will see you coming.

-On top of team fights, after the initiation, with as many of the enemy team as possible.
-To save a tower that is savable.
-And (very seldom), to get to an enemy tower more quickly, in order to backdoor.

When to NOT Ultimate:
-On single enemies
-If you would end up facing alone
-Before an initiate


Basically, just use common sense.
Know when to use your ult according to these simple rules. After you use your ultimate, their will be a small window you can use to use your Aegis of Zeonia. Use that time to activate it and select an enemy player, focusing on the the carries, and dish out a full combo on them.

Please, if you can, rate according to what you think this build deserves.
I am open to all critiques and criticisms, so don't be shy. :]

I hope you have enjoyed the Pantheon, The Artisan of Solo Top, champion guide!

01/01/12
-Updated item build order, thanks to: mrlonewolfer and BoxingTheStars.
-Added other skill orders, and paths you can take according to roles you wish to play.
-Added options for quintessences, and explanation, as it was absent from the guide.

01/14/12
-Added more options for glyphs.