Pantheon is one of the two new heroes released in the last patch. He's classified as a melee DPS, and while this is accurate, he's not in the same league as champs such as Master Yi or Jax (at least, not yet). However, this doesn't mean that he can't hold his own. Pantheon is well equipped to win almost any 1v1 fight, and he has the means to turn the tide of a team fight. Just keep in mind that he's not well suited to becoming the sole carry, and you'll be jumping poor saps for easy kills in no time.
SUMMONER SPELLS AND MASTERIES
My Favorite Spells
Exhaust is a great choice for Pantheon, mostly for the slow. I always take it along. I also like Ghost as it helps pursue weakened enemies, flee from ganks (though hopefully you won't need to), and most importantly, tower dive with little to no risk. I'll explain this later.
Flash is never a bad choice, but I find Ghost just works better with how I play Pantheon. However, feel free to take it if you prefer. Fortify is that spell that everyone wishes someone else took when you need your tower to hold just a bit longer, and since Pantheon doesn't need Teleport, you can fill that need. The extra creep damage is a nice bonus. Ignite is a favorite among many DPS players, and with good reason, so it's not a bad choice either.
You want 21-0-9 with Pantheon. This is almost non-negotiable. He's a very offensive character, and benefits greatly from offensive masteries. Some of the points can be spent according to preference(especially the utilities), but for the most part this is what you will want.
SKILL EXPLANATION AND ORDER
Pantheon's passive is ridiculously useful. It will save your *** more times than you'd think, give you offensive options, and it recharges very quickly. My favorite use for it is tower diving- the passive will block one tower shot, and thanks to its short recharge and your W skill, longer dives become a possibility. Generally you won't take too long though.
I seem to be in the minority here, but I like this move quite a lot. It's not too much stronger than a normal attack until late game, but it's cheap, has a short cooldown, and is a great harasser, especially early game. Nothing scares a squishy lane rival like losing a fourth of their health because they got too close to you. Later on this is useful for pegging runners and doing some extra damage after jumping a target. Hell, it's good for pegging runners the whole game.
W-Aegis of Zeonia
This is what sets up kills for you and your teammates. The damage isn't great, and it scales with spell power, so it's not going to get any better with this build. However, the damage hardly matters, because you want this for the stun. 1 second isn't too long, but it's enough for a Heartseeker Strike and whatever else your team throws. Levels in this lower cooldown but don't increase cost, so I like to level it in the laning phase where the damage is still decent and mana is tight.
The passive 100% crit chance on enemies with 15% or lower HP that this skill gives is useful for enemy champions, but even more so for last hitting creeps. This is what is going to make Pantheon his gold. The active, however, is what's going to get enemy champs that low. Early game this isn't very powerful, but later on when you have a ton of attack power, your victims are going to **** their pants at the thought of getting hit by this. The fact that it hits in a cone means you can hit multiple unfortunate enemies with it, and farm entire waves of creeps very quickly.
Just to put how much this can hurt into perspective, at level 5 this move does 30% of your attack power 5 times, and 60% instead of 30% if it's hitting a champion. This means you can do 300% of the damage you'd normally do in a heartbeat!
Keep in mind though- this skill is not very good until around mid game, it's fairly expensive, and even at level 5 its cooldown is LONG. You're almost never going to get more than one Heartseeker off in a fight, so make sure it hits by stunning with your W first.
Here's what makes Pantheon such an odd melee DPS. Anyone with half a brain is going to get as far from the center of your landing zone as possible. You're rarely going to do the full damage to anyone. However, this doesn't mean that the move is useless. You just have to get creative.
In the same way that Gangplank's ult can, Pantheon's ult can trap enemies between a rock and a hard place, or in this case, your team and a painful 35% slow. The AoE is really big on it, so you can block entire lanes or paths easily. Dropping on top of an enemy group in a team fight can be a huge tip in your team's favor, assuming they're clumped together. You can ensure this clumping to some degree, because during the landing phase of the ult you're technically located at the landing site, meaning your summoner skills can be used from there. If you weren't sure about taking Exhaust for some reason, that should seal the deal.
Keep in mind though, that you spend about 4 seconds channeling and 2 seconds warning the enemy, so try to predict the enemy's movements for those 4 seconds as best you can.
Try to save this one for team fights, unless you really need to get somewhere immediately. And for the love of all that is decent, don't use this to farm creeps. You have your E for that. Don't be stupid.
Pantheon is easy to buy for because he needs weapon power more than anything else. I like to start out with a Doran's Sword for early survivability/power and a health pot. When you head back to base, grab a Chalice to help Pantheon's mana problems. With this, as long as you don't constantly spam skills, you won't run dry nearly as often. Grab Boots of Speed as well, and upgrade to Berserker's if you can afford it. If not, the upgrade can wait.
The next item you want, whether or not you could afford the upgrade, is a Brutalizer. Generally this is the point in the game when you're going to need to start jumping people, and this'll help a lot. After you get it, upgrade your boots if you haven't already.
Here's where opinions tend to differ on what to buy. A Frozen Mallet is a great choice, but expensive and not essential. The slow is nice though, so consider it later on.
No, what we want are B.F. Swords. These bastards give you 50 freaking extra weapon damage a pop, and that's a huge difference for anyone, especially Pantheon. You can upgrade them if you want, but try to get at least two. If the game is still going at this point, sell your Doran's and get another. It's simple, and not very clever, but I'll be damned if it isn't effective.
Assuming you have my above listed build, little can stand against you for more than a few seconds. Towers, inhibitors, and even nexuses may as well be made of wet paper. Your stunned victims will be torn apart by your E, and if they limp away, gored by your Q. You may be squishy as hell, and very vulnerable to stuns and blinds, but this is why you work with your team. Generally I end my games with a KD ratio of about 1.5:1, but with almost twice as many assists as kills. You can feed your team kills all day long with this build, and get a fair amount yourself.