Hi, this is my first guide to be posted for Moba-fire and I wanted to share my build on one of my personal favorite champs. In all honesty, when i first bought lee sin I was very disappointed, he was nothing like i expected. However, the more i used him the more i discovered what a great champion he is.
Lee Sin is viewed as an underpowered champ that doesn't even closely live up to the hype. I, however, think that he is a great champion with lots of potential but requires more skill than most assassins. He has amazing damage output early game. His q makes last hitting low hp champions a breeze while also making him extremely hard to escape. Lee Sin skill combos allows him to jump in to deal damage and escape to safety in an instant.

For runes I use a pretty typical AD set up. Armor penetration marks, Hp Per level seals, Magic resist per level glyphs, and armor penetration quintessences. Lee's base health totally blows, I find using hp per level runes helps lee stay in the lane longer and increases survivability much more than flat armor or armor per level. The armor penetration runes make lee sins abilities and auto attacks devastating during the laning phase. The magic resist per level helps lee sin survive against ap heavy teams because burst damage is not good for the blind monk.

I use 21/0/9 to maximize damage output and experienced gained. The magic penetration increases tempest/cripple damage output as well as Madreds blood razor and Wits end. The armor penetration and attack bonus masteries amplify the runes I use. Attack speed helps farming and I leave the critical masteries at 0 because my build is more reliant on steady magic damage while bursting high amounts of physical damage with skills.

For items, I start off with a longsword the extra 10 attack at level one makes your Q hell of alot deadlier and an hp pot. Early on, Lee sins damage is already incredible. So building a phage will help with survivability add a chance to slow and slightly boost his attack power. Next you grab boots and upgrade it to whatever best counters your laning opponents. If your against CC merc treads are the best choice, but against squishy champions such as teemo, yii , and etc I prefer berserker boots to help farming in the lane and recover hp with ironwill. Next off is life steal, a vamp scepter and your iron will buff makes healing to full hp a breeze. After those items. its time to start saving for a BF sword which will as soon as possible be upgraded into a blood thirster. Wits End is your next purchase, start with the Re curve bow for much needed attack speed. Upgrade as soon as you can, to have an extra 42 magic damage per hit, decent magic resist, and shred 42 mana off your victim with every attack. Next is the Madred's blood razor, great for killing baron and those unlucky bastards that stacked hp. At this point, you should be able to mop the floor with anyone 1 on 1, have great burst for team fights, and easily kill anyone trying to run away. Your final items are to solidify what you've done so far. A frozen mallet will not only give you a huge boost in hp but also insure no one runs away while you bash them in. Last but not least grab the last whisper it'll help you take down the tougher enemies that have been building armor.

Sonic Wave/ Resonating strike an extremely long ranged skill shot followed by a leap kick of doom is your best friend. Its a great for harassment, checking bushes , closing the gap in fights , epic escapes over the wall to neutral minions, chasing down runners ,and well .. i could go on forever. Its an extremely versatile skill and is the heart of your combos max it out first. Safe Guard / Iron will is your survivability allowing you to leap to friendly targets instantly at decent range and the follow up is a buff that increases your armor, life steal, and spell vamp. This skill is priority number 2, it allows you to heal to full health instantly off minions and the shield can save you and your teammates lives. Tempest / Cripple is your E skill, its a short ranged AOE that deals moderate damage and reveals. Great for farming and revealing those pesky low hp stealth champions ( akali , teemo ) The second effect slows both movement speed and attack speed of those hit by tempest. Useful both for chasing ,escaping, and murdering dps champions in 1 on 1 fights. This skill is already effective at level 1 so its priority is last. Dragons rage your ult is a extremely power great as well as disruptive. Its similar to Alistar's head butt but has the added effect of knocking up and dealing damage to anyone hit by the champion that was kicked. Max this skill anytime it becomes availible.

Ghost and exhaust are great spells for lee sin b/c like his champion skills they are great for both chasing and escaping.

In conclusion, Lee Sin is an extremely versatile champion, He is great at laning and also able to jungle. Excels at dealing damage and jumping out. Murders Dps champions and squishies. My goal with this build is to make Lee sin deal strong consistent damage to both tanky and softer champions and using his skills to finish them off. I also wanted to give him a good amount of hp, armor and resistances to increase his viability in team fights.

Pros-

Has magic damage for dps and physical damage for skill burst damage forcing enemies to buy both magic resist and armor
extremely hard to run away from
1 on 1 fights should be a breeze
Good amount of hp and resistances
very good at laning, jungling, and pushing towers

Cons

Damage is spread out so output is less than that of a pure a/d
If focused falls pretty easily
items are expensive and rely on early game kills
While laning, Partner must be able to put out a decent amount of damage and harass

Farming is fairly slow until about level 4 when you get tempest/ cripple. at levels 1-3 focus on last hitting minions and harassing with sonic wave. At level 4 self casting safeguard /iron will then using tempest well heal you significantly as well as damaging surrounding minions making last hitting easier.