This is a build that I've been focusing a great deal over time. It's basically a tank build for lee sin that will prevent him from dying in most any circumstance. The combined armor and magic res will keep damage to lee sin at a minimum while the thornmail will force melee heros to kill themselves. The frozen mallet and lee sin's own slows will force melee heros to fight him due to the inability to run away. Thus allowing Lee Sin to really just pound away at his leisure until they decide it's not worth it to fight him anymore. This allows you a huge psychological edge, you may not be the insta-kill champion but you are the, "stand there until my enemy dies" champion.
*Note*
This build does have one dangerous flaw, all the items involved cost fairly high amounts of money which means that while you are building you can be susceptible to enemy attacks while starting. Play it safe at the start and spam your tempest like crazy for minion kills.
*Other note*
This build is still being tested in various stages so do not be afraid to adjust it based on the enemy team, building a force of nature before the thornmail for fighting more magic based teams and so forth.

The only point behind this build is to make lee sin indestructible. The combination of armor is focused on high defense and insane health/health regen. The atma's is simply to give lee sin a basic boost to attack near the end because if you have time to get around to it, chances are you need the extra attack power.

It may seem a bit random but basically you want to spam tempest as much as you possibly can. The only reason to get safeguard early game is for the bit of lifesteal it will give you, allowing you to lane a bit longer then usual. In between blasts of tempest you want to work sonic wave in as well. Using Lee Sin's powers often will let you kill the minions very quickly and if you space them out he will recover any energy he may use. Dragon's Rage is nice for keeping enemies away from an ally if they get pinned but Cripple is the most useful for it's slowing ability.

I'm adding this section because I get that this is a weird build for Lee Sin and some advice on using it may be welcomed.
Facing a Main DPS Team- The main point that must be remembered when laning Lee Sin is that his most effective capability is his ability spamming, specifically tempest. I always start with tempest because it allows quick minion kills and also serves to keep other melee characters at a distance. Space out tempest and cripple so that you get the full effects of the attack speed gain from your abilities and don't lose any energy from using your abilities. If for whatever reason you are in danger of being ganked you also have the option of an easy escape by crippling the enemy and then flashing away.
Next I get safeguard or sonic wave depending on how aggressive the enemy players are. If they are constantly trying to wear you down then go for safeguard. The shield is small but even the small amount of damage absorption can help and the life steal on its secondary ability can make you a devil to wear down.
If the enemy is going lighter on the offense due to your tempest spamming or any other reason then go with sonic wave. The added attack ability allows you to better employ the attack speed bonus and either increase the speed of minion kills or allow you to hit nearby champions with it to keep them back.

Now for all cases in this build you will want the frozen mallet first. This may seem almost suicidal in some circumstances but the added health, damage, and slowing affect on it added together with your abilities makes you remarkably difficult to deal with early game. The slowing affect can be used attack, save another team mate, or to run if necessary.
As for any character playing tank against a DPS team, thornmail is your absolute best friend and should be bought after frozen mallet so that enemies who fight you won't even be able to run away after they realize that they are killing themselves attacking you.

All in all, this build has served me well over pretty much any gaming scenario. One thing I would like to get straight though is that this IS a difficult build to pull off. You will need to try it for some time to get a feel for just how much each item purchase and ability upgrade improves Lee throughout the battle. But to those who do manage to learn the ebb and flow of this build you will find that 1v1 is easy and that even 3v1 can be achieved without to much difficulty.

Hope you like it, I will be updating this further but if there's anything else you'd like me to include in this guide please comment. I have lots to tell but I need to know but people want to know.