Not Updated For Current Season
Pantheons key weaknesses:
1. Cool-downs (really why so long riot?)
2. Mana Problems
3. Low Health
Although this build does not entirely solve these problems it aids in minimizing them.
1. The rune build + mastery build + brutalizer reduces cool-downs by 24.85%, indeed it almost takes out the need for the brutalizer at all, it just gets left in the build because it can still help out Pantheon and is a fairly standard item for AD champions. But using this build the brutalizer can be skipped in favor of a faster bloodthirster, because the armor penetration provided is only adding to what is already obtained through the marks of desolation.
2. Mana will most likely still be an issue with Pantheon, but the higher level he gets the less problem it will be as the mana regeneration climbs to 24.2 mana per 5 seconds at level 18. In addition the extra experience and regeneration offered through masteries should aid slightly early on. Regardless in my experience it is harmful to Pantheon to spend 400+ gold on mana items instead of rushing damage items.
3. Through the Quintessences Pantheon will gain about 100 health through this build. This can not be stressed enough! One hundred health in the early game is incredibly essential to the survival and stamina of a champion in a lane. After this laning phase as Pantheon begins to look for ganks and team battles start health will become a problem agian, ideally the bloodthirsters will allow Pantheon to stick around towards the mid, more likely late game.
Overall this build seeks to inform and address players about what I deem are 3 of Pantheon's greatest weaknesses. The mastery sequence is not filled out because like the item's it is best left up to the individual player; you already know how to play Pantheon a little, that's why your reading this right? The sequence of the build is not exact because it is best left up to the player/situation in most cases, similar to the skill sequence. Keep in mind the brutalizer and sword of occult are replaceable and situational respectively, while the boots of swiftness and bloodthirsters are essential. But, ideally the sword of occult will allow Pantheon to strut around as he pleases. Last of all the summoner spells are used for a mixture of escape and ganking ability, flash can also be used in combination with exhaust when champions are running away. Also don't forget to use exhaust to blind the enemy's major physical damage champion in team battles!
Hopefully even if you do not agree with or follow this guide it will set you to thinking about how to solve Pantheon's weaknesses without dishing out gold for items... Maybe if enough of you do well enough he will get nerfed again, eek!
I forgot to mention that the lizard and golem buffs are very beneficial for Pantheon in solving the mana/cool-down problem as well as granting him a better attack. It is often beneficial to stay behind during a team push and grab a rune and use sky-fall as a means to join the battle or catch up.