Spider-Man has been one of Marvel Comics' hottest commodities for years. The face of the company, the wise-cracking wall-crawler has featured in nearly every title Marvel has put out, and seems to be on a first-name basis with nearly every character in the sprawling fictional universe. If you'd like to bring a set of spider powers to your Pathfinder table, then this guide should help you nail down some of the big strokes in creating your own high-fantasy Spider Man.
For character guides to other members of the Marvel Universe, as well as Gotham City's vigilantes, and the cast of Game of Thrones, take a look at the Character Conversions page on Improved Initiative.
Also, have you ever wanted to know why superheroes wear their underwear on the outside? Here's your answer!
With Great Power...
Race, Attributes, and Traits
For practical reasons your Spider-Man build should focus on dexterity, wisdom, and strength. While human is a fine race for this build, elves and drow also work quite nicely. You can never go wrong with humans' bonus feat and skill, but low light vision and skill focus, or dark vision and a race where one could be personally chosen to serve a spider goddess are also quite snazzy. Especially if you want to make a cult of evil Spider-Men (you're welcome, dungeon masters).
When choosing your traits, you should focus on what will be most useful to you. Reactionary (+2 to initiative) or Warrior of Old (elf, same bonus) are good for characters who want to go first. Here's a whole post about why that's a great idea, by the by. Other traits like Crowd Dodger (+2 on acrobatics checks to enter another's square or to avoid attacks of opportunity), Soaring Sprinter (+2 on acrobatics checks to maintain balance or to jump), Alchemical Adept (+2 on checks to create alchemical items, and when you fail by 5 or more but don't roll a natural 1 you don't ruin your raw materials. This one's great for those building their own gear.), or Dangerously Curious (gain a +1 on use magic device checks, and use magic device is always a class skill) are all good choices as well.
Just remember, traits that never come into play are traits you'll regret taking. When in doubt, pick a bonus you'll get a lot of mileage out of.
Given all the high-flying acrobatics, ridiculous jumps, and the blue-and-red tights, Spider-Man's obvious class of choice is monk. Not just any monk will do though; the Flowing Monk (Ultimate Combat 58) is perhaps the best choice for Spider-Man. You lose stunning fist, fast movement, your second level bonus feat, purity of body and diamond body, but what you gain is the ability to redirect and trip opponents who try to attack you, as well as dodge bonuses that can make you look like you have precognition. It's the closest thing to spider sense that isn't just acting in the surprise round.
Here's some more details on class abilities.
Reposition, gained at first level, is going to be your bread and butter. This ability allows a Flowing Monk who is attacked in melee by a creature he threatens to use an immediate action to make either a reposition or trip combat maneuver. If the maneuver is successful the enemy is sickened for 1 round (a Reflex save of 10 + 1/2 monk level + monk's wisdom modifier halves the duration) +1 additional round at 4th level and every 4 levels thereafter. If the opponent was charging or using Power Attack then the monk gains a +2 on the maneuver and a +2 on the DC. For those keeping score it's a lot harder to hit someone when you just got knocked flat on your backside.
Unbalancing Counter, gained at level two, says that creatures struck by a monk's attack of opportunity become flat-footed until the end of their turn, though a Reflex save with the above formula negates the flat-footed condition. Yes attacks of opportunity are fairly rare, be patient, this will come into play later.
These monks also gain Flowing Dodge, granting them a +1 to AC for every adjacent enemy, and Elusive Target which allows the monk to apply his Reflex save against enemy attacks for lessened or no damage for the cost of 2 ki. You don't need armor if they can't hit you in the first place.
Aside from these changes the Flowing Monk gains all the stuff you're used to from a monk. You get your wisdom modifier added to your armor class, you gain ki points, unarmed strike damage, and the ability to use your monk level on combat maneuvers. That last one is actually pretty important, especially if you want to be effective when it comes time to trip or reposition your enemies.
The three most important feats you'll have as a Flowing Monk are the Crane Style feats: Crane Style (monk 1st), Crane Wing (monk 5th) and Crane Riposte (monk 7th). Crane Style states that you only take a -2 when fighting defensively, and you gain an additional +1 to your armor class. Crane Wing states that once per round when fighting defensively you may choose a specific attack and gain a +4 dodge bonus against it. If you are using total defense you may deflect one melee weapon attack completely, provided you're not flat-footed and are able to act. Crane Riposte states that you only take a -1 when fighting defensively, and that after you block an attack with Crane Wing that you may make an attack of opportunity on the individual who swung at you.
That's pretty badass, wouldn't you say? Note that Crane Wing allows you to make attacks of opportunity; that's where this feat tree feeds into your ability to make enemies flat-footed.
Of course your arachnid-themed monk can always use more feats. Dodge is a great feat for instance, and Improved Trip (Core 128) along with Greater Trip (Core 126) make a Flowing Monk quite dangerous. These feats also require Combat Expertise (Core 119). It's also a good plan to have things like Deflect Arrows (Core 121) to keep your monk as safe and projectile-free as possible.
What order should you take all this in? Well that varies depending on what you want to do. Here's a suggested progression, though you should feel free to change it up the way you want.
-1st level feat: Crane Style
-1st level bonus feat: Improved Trip (taken off Flowing Monk list)
-3rd level feat: Dodge
-5th level feat: Crane Wing
-6th level bonus feat: Combat Expertise
-7th level feat: Greater Trip
-9th level feat: Combat Reflexes
-11th level feat: Vicious Stomp (Ultimate Combat 123)
Are there more feats you can take? Of course there are! Can you take them in a different order? Why not, it's your character! This is just a suggestion for those who want something to start-off with.
EDIT: Another feat you may wish to add is Spider-Step (Advanced Player's Guide 170). It lets you walk across walls or ceilings at half your slow fall distance. While slippers of spider-climb will be more reliable, this is a great feat for those who want an inherent wall-crawling power.
Spider-Man's power set is pretty impressive, but he is always prepared for the worst with the right equipment. Here are some things you'll need both thematically, as well as practically.
Tanglefoot bags are your friends, especially at lower levels where enemies are likely to wind up glued in place. If you have a spider-sac, you can squeeze it and shoot out a 10-foot rope to either ensnare your enemies like a lasso, or to swing through the air. Combine that with a spring-loaded sheathe, and you've got a ready-made set of web-shooters. Combine that with the monk's slow fall, and there's no drop too treacherous for you!
There are other great alchemical items listed in this article here, but magic can definitely be your friend as well. Slippers of Spider Climbing (Core 530) can provide you some of the wall-crawler's abilities, especially when use of the climb skill is out of the question. The usual items of the monk's belt, bracers of armor, an amulet of natural armor, a headband that increases your wisdom or a belt that increases your strength and dexterity, will also be great to have on hand.
Lastly, don't be afraid to use a few wands. Web is definitely your friend, and if you can snap Mage Armor on before you go out adventuring, then more power to you. Lastly, don't forget your ring slots. Jump bonuses, acrobatics bonuses, and even a shield bonus are all great things to have on hand... so to speak.
Putting it All Together
What you have here are a basic set of mechanics; a skeleton frame. What you do with it from this point onward is up to you. Do you stick with the drow, and build an avenger trained in the ways of infiltration and non-lethal capture? Do you add a few levels of ranger for more outdoor utilitarianism? Give your stealthy spider a gun filled with sticky shot that can be used to leave enemies bleeding and covered in resinous tar? Is your wall-crawling, rope-slinging adventurer a reformed thief? A protector of a city? A servant of hidden gods whose orders one might only guess at? That, my friends, is your call. I've given you a start on the how... now tell me the who, the why, and the what.
Oh, before we depart this build does have weaknesses. Anything bigger than Large size is going to give you fits because it can't be covered in goo, and you can't trip it. Flying enemies are going to be a huge problem too, as reaching them can be a pain. Anything with four legs can be a trouble as well. This build isn't meant to do damage; rather it's meant to knock as many foes onto the ground as possible and to restrict their movements so they waste time rolling around on their backs or pulling themselves out of webs. Heap on enough negatives, and even the biggest fight will be over in less than a few rounds, though.