Just a little about myself before we get to the nit picky stuff. I have played over 600 games (not enough to say I'm pro, but I'm pretty good), and clocked almost 600 hours of play. ANYONE WHO WANTS TO USE THIS BUILD, I'LL SAY IT NOW AND AGAIN LATER, I BELIEVE THIS RUNE BOOK IS CRITICAL TO MY SUCCESS, IF YOU DON'T HAVE THE RUNES, DON'T USE IT
Master Yi is a character who recently, I have fallen in love with. His carry ability doesn't actually have any starting time, by lvl 4 you can be running around getting massive kills, and by 6 you should easily be clearing out lanes, but more on that later. I usually game with friends IRL or close online friends, but I do have a few groups I game with outside. Master Yi is in no way my main character, and I usually tank, but recently I've been doing extremely well with him, and figured I'd share my success (half of it might be in my AD sion runebook, IDK)

My runes, now this is an odd book for Master Yi who starts in a jungle wouldn't you say? I have found that beginning with that 14% crit chance is very useful for jungling. Did I say jungleing? Yea I did, its what makes master yi so fun to play. The unpredictability of master yi flying out of the forest and hitting you with red buff is a sight to behold, his 7 eyes intently focused on slaying you and your lane partner often leaves you dazed and enraged (if you play Sion this is a hilarious pun, in itself Ironic because I use my sion runebook). The magic regen glyphs give you a hefty mana boost late in case your blue runs out while in the enemies base (you should easily be able to get outta there with Highlander if you need to). The crit chance is just high enough that you will hit a crit often enough to slay jungle minions efficiently. The attack speed is something that is such a major boost to your early game, and essential to jungling as well, because lets face it, you would get wrecked by those golems without your smite, and that attack speed + crit chance.

I'd say pretty standard Jungle Yi spells, except that Fortify. Fortify is such an odd spell on master yi, it is a spell you see tanks taking all the time, and is considered almost useless in a game vs skilled opponents. But there are two reasons I chose it instead of one of the many spells. The minion damage is really nice, after ganking a lane, you can easily heal on the creep wave sweeping through. Second it gives you a psychological advantage of the enemy team thinking you are a nub until you fly out of the forest and double kill... then fly back in like a rabid chimp that just stole its bananas back. It can tear a team apart from the inside when the arguments begin about how that nub yi just double killed bottom lane, and how they are feeding. Oh not to mention the nice, you can't kill my turret for a while, so your "UBER PUSH TO SAVE THE GAME" just turned around into a "at least we blew up a turret before yi wrecked us"

The skill sequence could possibly go alpha strike and wuju style alternating, but I prefer this way, as you have a higher level wuju style first. Normally a jungle yi would get alpha strike, but you stake your claim on the jungle by wrecking every lane that is near it. And since a champion kill is much more rewarding you will be ganking out of the jungle a lot. The reason we jungle is 1) if done right you can level as fast as solo lane, and your allies get a level advantage too. 2) not knowing where you are is terrible warfare on the enemy team psychologically and physically, they have to decide between preventing you from pushing them out and/or killing them and buying wards and skipping an item upgrade earlier which will leave the lane crippled.

I believe the pictures are self explanitory, but you start by buying a vampiric scepter, and then working your way up to stark's Fervor, then berserker's and so on.
You may end up building in a different order if you get lucky crits, or not, and weather your alpha strike insta kills anything or not. Now, there is one thing not mentioned at the top. IF, and that is a big bold IF<---(just a big if), the game lasts long enough, or you have the gold available after the rest of the build is done, you can, in this order, sell berserker's and buy a second Phantom Dancer, and then sell starks for a Bloodthirster.
[Edit, added after comment]-The reason I get a second infinity edge is for the damage, and crit chance, it puts me at 99% in game, and gives me damage, where you could trade the trinity force for a phantom dancer and get a bloodthirster instead of the infinity edge (I do this with nocturn) with master yi and alpha strike +wuju style+ highlander, you get a lot of Trinity force activations, which means more burst damage on their carries, which means you take out their dps before they can react.

This build is not for everyone and I'll say it again now ANYONE WHO WANTS TO USE THIS BUILD, I'LL SAY IT NOW AND AGAIN LATER, I BELIEVE THIS RUNE BOOK IS CRITICAL TO MY SUCCESS, IF YOU DON'T HAVE THE RUNES, DON'T USE IT
Here is a list of pros and cons

Pros
1. Earlier game carry capability
2. More exp for your team
3. You provide a valuable psychological aspect against any skilled player on the enemy team, forcing them to play extremely defensively to prevent getting killed for pushing or being punished for killing an ally.
4. Wicked sick multi-kills ranging up to penta-kills

Cons
1. All that normal time yi has trouble building to carry is squeezed into a 7 minute window of a struggle of life or death (could be a pro though)
2. One lane early game will have to fight to the death for life also
3. Risk of being called a nub for the first few, lets try this out games, and a nub for picking those spells.

Okay this is the most important part of the build. You start at the 2 mini-golems. You do NOT activate Wuju style to kill them, sufficing simple brute force and a well timed smite. You will have half health or more (depending on those crits), You will be lvl 2 and have alpha strike, now comes the moment of truth. You alpha strike the wraiths starting on the Blue greater wraith. After you land from your alpha strike activate wuju style and kill the blue wraith first, then working down to the lesser wraiths one at a time (if smite comes up don't use it). Then you go to the dogs, judge your health wisely though, I died to them once, after a series of unlucky non crits or insta kills, if you have 1 and half bars or less you are at risk of death, if you take them on wait for wuju style to come up again, then alpha strike the larger dog, and once again again activate wuju style to kill it an its pups. Put your new point into wuju style again. Now recall and buy your Emblem of valor (increasing your lifesteal by 5% and giving you health regen. Now start by working through in the same order in the jungle, mini-golems, wraiths, and dogs. After you finish dogs this time, make sure your smite will be up very soon (15 sec or less), (you should be lvl4 and have 2 points in Wuju style and alpha strike), then judge your health, if you are at less then 2/3 recall, otherwise, challenge the blue buff to a pokemon duel... I mean to a fight to the death. Initiating with alpha strike and focusing the golem, using your smite and activating wuju style, you will barely escape with your life, but you now have blue. Recall and buy boots of speed. Then go kill Red buff, and you are ready to tear a lane to shreds. Remember to jungle whenever you can and keep your buffs up, because they are an early game factor into making you OP.

I cannot stress this enough. A well coordinated team is the best possible thing to have. I even will team up with friends who are lower level (with higher level friends, and go up against lvl 27-30's) just to have the advantage of knowing things on the map, it helps to be in a voice chat of sorts. Your first gank should be coordinated with a team lane for the early pushing, but if both bot and top are at near full health, coordinate with mid. You should make sure your team is comprised of a few disables/silences to prevent blinds and stuns on you when you jump in. You should have an efficient tank, who will get them to waste their stuns and any other debuffs on him, but you can do without the teamwork, as long as you have semi-competent allies, who can hold off the end until you can just constantly ace the enemy team. (I recently played against Tyrindamere, Xin, Jarvin, Kat, and Pantheon; they were wrecking us, but the fortify held them off until about 45 minutes in, and I aced them while they had Baron. It was an extremely tough game, with a nasus who left part of the way through, then came back later. We had 3 turrets down and they had 6, and then we eventually pushed to win).
Don't forget that you play a part in this team too! Your allies rely on you to help them out of trouble in lanes, and cover if they have to recall. In exchange for kills and being meat shields the expect you to carry them to victory and prevent them from dying as often as possible. You also should know how to play master yi, if they aren't afraid of you, then you aren't going to be much use. One of your greatest strengths is causing more fear than fiddlesticks.

This build comes with many advantages to it. One is the early game leveling speed. You can out-level mid if you do really well, or you can level with mid if you are only doing ok. This build also has a good synergy with master yi and his passive, you build attack speed first, so that your passive can help, and you get more chances to crit, as well as easily taking down even the tankiest early tank, and late game you do massive crit damage, plus slows. It also has synergy with his ultimate, the only character who will outrun you will be either rammus or Dr. Mundo, any others can ghost and you still will probably outrun them. The only thing to watch out for is a Thornmail on a high health character. If you see a thornmail, kill their allies, and keep them entertained until your allies show up. In the game I mentioned earlier the Jarvan had a lot of health and a thornmail, but couldn't really hurt me. So I simply killed his allies, and let teemo and cho kill him. Master yi also has Wuju Style which means that attack speed effectively increases the damage that skill can do early especially.

This build is not for everyone, and most definitely not if you are new to Yi, but you will find yourself in love with it if you are already an experienced player, and find that the capabilities it brings to the table are second to none (okay maybe a few, but this build is for funtertainment). So if you are a fan of having fun AND winning games, like this build up top after commenting below!