Pros

-Massive Damage output

-Shreds enemy tank armor

-Great Carry, Ranked or Un-Ranked

-Amazing range

-Passive can harass enemies

-Great KS'er

-Its a Chick with a gun. thats all you need to know

Cons

-Hard to chase if you cant hit 90 Caliber Net

-No real good escape (90 caliber net doesn't slow long enough or push u back far enough)

-Low Hp

-Low Mp

-Extremely weak to ganks

Caitlyn is a high damage character and can have good attack speed and critical. She is one of the few champions that can outrange the turret with Piltover Peacemaker . This Caitlyn build is specifically based on her extremely high damage and her amazing range with Piltover Peacemaker and Ace in the hole

Quintessence's-

I went with quints of desolationGreater Quintessence of Desolation ,because Caitlyns' ability to destroy enemy tanks in-game. Some tanks stack high armor and can be troublesome though for example tanks like Rammus . So with the armor pen quints(and marks) to tear through enemy's with high armor and can prove to be extremely useful mid to late game.

Marks-

more desolation runes for tearing through enemy tanks armor and taking down people with 3k hp in seconds. Pretty useful in mid to late game early game desolation runes dont prove to have much need for no one has very high armor but the late game boost is amzing.

Seals-

I got seals of fortitude because though Caitlyn has a very high damage output she has very low health. So for the seals that specialize in defense i put fortitude runes to help Caitlyns low Health problem to be solved somewhat in early to mid game situations. By late game the runes will prove to be less useful ,because you should be killing most enemies before they can even get to you.

Glyphs-

for glyphs i got the greater glyph of replenishment Greater Glyph of Replenishment because another of Caitlyns few problems is her mana depravity. So you should be getting 2.7 mana a second at lvl 1. Now this may not seem like a big number but heres a hypothetical situation for you. Your Caitlyn you have 50 mana and your fighting a jax with 100hp left and he isnt recalling. in less than 40 seconds you will have enough mana to use Piltover Peacekeeper Piltover Peacekeeper and take him out.

Mastery Tree

For masteries i tend to go 21-0-9 with 21 in attack masteries and 9 in utility masteries. I go into attack masteries by first giving 3 into deadliness and then an extra point into Archmages Savvy. Then go 4 into Alacrity you do this for the extra attack speed for your Youmuu's Ghostblade and berserker greaves . Then i go 3 into Sunder for extra armor pen. Then 3 into Brute Force for that extra attack damage and 3 into Lethality for your crits. Then last but not least 1 into Havoc For that 5% extra attack damage overall.

For my 9 points in utility i go 3 into PerserverencePerserverence for mana regen to help out my runes. and 1 into Good Hands for no real reason except i needed to use one more to get to the next stage and i dont plan on dying but if you do it comes in handy for reduced death time. next i put 4 into Expand MindExpand Mind for more mana to fight against Caitlyns mana depravity. then i put the extra point into Meditation . Though its only one point it helps more than you would think increasing your mana regen by .33%

I go Flash and Clarity for several reasons each.
-For flash i get it because although Caitlyn has the 90 Caliber net move she doesnt really have any form of escape which can be troublesome for a champion with such a low base health. Another reason for me getting flash is that caitlyn can be an excellent ganker. Just go from bot or top(explained below),maybe even mid. Into the brush behind an enemy champ trying to get away and flash over and use piltover peacekeeper to finish them off.
-Clarity i get for the obvious reason and that is that Caitlyn is mana deprived and when you just need that one last shot and your out of mana it tends to annoy you that you could have had a kill if you didn't run out. Clarity can also be used for escaping purposes. I know what you thinking but let me give an example. Say your running from someone and you have no mana and flash is on cooldown. Lets say they have an obvious advantage in movement speed. You could use clarity then use 90 caliber net to slow them and get ahead. You could repeat this until your to safety.

-Start off by grabbing a Long Sword and a potion Health Potion. Now heres where this build for Caitlyn is going to stray from the path. I suggest you dont go mid. Although many people say Caitlyns a great mid character and has superb rang to push in mid. I tend to disagree on some points. Going into the bottom or top lanes with a close ranged melee champ can get you fed quicker than i have ever gotten kills in mid. Even though she is a great mid char i believe you will get more kills by laning top or bottom.
-On your first return grab a brutalizer and if you have enough Boots of Speed too.
-Next get you Youmuu's Ghostblade and i know what some of you may think but youmuu's is a great item for Caitlyn due to its dmg Cooldown Reduction and its active. Now if you are not very use to using items that have actives like Youmuu's i invite you to get a Phantom dance instead and start off getting a Dagger not a Long Sword. Either way you will be a successful Caitlyn.
-As soon as you can go back to get your Berserker Greaves . Mainly ,because you will need the attack speed to keep you from getting killed by charecters that can slow you like Karthus,Dr.Mundo,and Nunu.
-Next start working on 3 B.F. Swords ,and do not buy the items that these make. Make sure you have ALL 3 before you get the next items. Theres a reason for this and its because the base attack damage that they give you will be enough to keep you from needing the other items, and late game all the items that these make will only cost around 1k each and you will be able to buy the quickly for a headstart on everyone else.
-After buying 3 B.f. swords you should get a Black Cleaver you need this item before the bloodthirster because it gives the needed boost in attack speed you have been missing until now. Not to mention you will have extremely high base damage form the other 2 B.F. Swords. If it seems that you cannot possibly live or continue to get kills you should replace this item with something defensive. i would suggest frozen heart/ if an enemy ad/dps champion is doing well. if an enemy ap champion is doing well i would suggest
-Next grab a Bloodthirster this is your main damage item and gives much needed lifesteal. Normally by this time you should have made your mark as one of the champions to be scared of, but once you get a bloodthirster you will be able to easily take out the strongest champ on the enemies team given that you have been relatively close in kills.
-Finally get your Infinity Edge . Now this item makes your crits which at this time is 35%(unless you went phantom dancer not Youmuus) which is not bad considering how fast you will be attacking. Not to mention the fact that your crits instead of doing 700-800 will now be doing 1.2-1.5k and if you get a crit when your passive headshot is active around the area of 1.7-2k dmg
-Lastly get a Frozen mallet for extra dmg and health not to mention that when you hit them you slow which gives great chasing. Not to mention now you have substantial health and will be able to tank out turrets and destroy them before you get to low by yourself. If you are feeling to low on armor or MR because an enemy champion is doing exceptional then i invite you to get or a depending on the situation. if two enemy champion are doing decently get a Gaurdian Angel

When going into a team fight while playing as caitlyn i tend to bring up the back of the team. I do this for strategic reasons. One of them being i do have one of the lowest Healths on the team. Another being i also have one of the best ranges on the team if not the best. Also if you have a tank in your team going to a turret and "tanking" it then you could quickly destroy it and prevent him from losing to much health. Try staying near someone who can stun if you have one. Being able to finish off an enemy champion while there stuned before they can do anything can be extremely helpful to your team, even if you do KS(kill steal) the champion who stuned them.

B- basic attack
Q-Piltovers Peacemaker
W-Yordle Snap Trap
E-90 caliber net
R-Ace in the hole

Ok i put this in here as a recommendation by Yukimaru. Now i would use simple basic attacks to start a fight ,but depending on the situation you should go with piltovers peacemaker. NO after initiating a fight try putting a yordle snap trap behind your enemy so once you start doing enoough damage to make them run they will get traped. Next use 90Caliber net, and lastly use piltovers peacemaker to kill them. and if it doesnt kill them then use Ace in the hole to finish them off. So your order should be B,W,E,Q,R or Q,W,B,E,R OR Q,E,R

Edited on February-7-2011 added a skill chaining section to depict how or when you should use a skill



Edited on May-4-2011 added thornmail,banshees,gaurdian angel due to the idea of here defense not being well late game. I tried it out and late game if your enemy champion are in a deadlock with you then you need to get one.

Caitlyn overall is a high damage character that is mana deprived but if played right can be one of the best champion in the League of Legends. Not to mention the great KS'ing ability of Ace in the hole. By end game your finisher will do enough damage to take out squishy chars like Sivir, Teemo, and Ashe. Although this build is not perfect i dont think there is one that is. Also if you have a Caitlyn Build that you think is good please put a link in the comments i would like to see and check to see if i need to make any changes to mine.