This build focuses on a high damage output with the slight AS boost that Master Yi needs to maximize his damage output. While I know the build offers little survivability and is very simple, personally I have never been beaten 1v1 by another Master Yi, even when I am underfarmed. I hope you try the build before criticizing it because it is extremely effective if used properly. Constructive criticism is welcome but please do not flame without at least trying my build first.

Sorry about the lack of pictures and color, my code abilities are a bit rusty and I wanted to post this build then refine it later on.

In my opinion you can use any runes that increase your damage output, or increase your survivability. Honestly you can use any runes and still do well but I prefer AS Marks because it helps you farm early game, and HP Seals with MR Glyphs for survivability.

I go for the 21/9/0 mastery tree because it helps your damage output and gives you a slight increase in AR and MR. Pretty self explanatory, but this can be changed to fit your play style if you do not like 21/9/0

Now it may not seem like it, but this part of my build was extremely researched, and I put a lot of time doing calculations and trying out different things. The start with boots and 3 HP abuses Master Yi's naturally high movement speed and can allow you to escape among other things much better. The triple HP as opposed 2 HP 1 MP allows you to stay in lane longer and as long as you're not spamming Alpha Strike every chance you get there shouldn't be MP problems. The double vampric scepter can be bought anytime, but I like to get them early on so you don't have to back as often. My first major item is Phantom Dancer because it gives you much needed AS and because of Wuju Style AD isn't as big of a problem as other AD champions. This followed up by two Bloodthirsters gives you amazing damage when you build up the stacks along with 50% lifesteal which allows you to pretty much 1v1 anyone mid game unless they are extremely fed or have a lot of CC. Items five and six and where my builds differ and although its only two items they greatly affect how you play.

For the first build you rely less on the AS boost of highlander and rely more on the 60% crit you get from the double Phantom Dancer. I don't like this build as much but it was my original build and it is slightly easier to play so I figured I should put it in. There are quite a few items you can get for item six depending on your situation.

Infinity Edge: This can be an extremely effective item when combined with the double Phantom Dancer as it gives you 85% crit chance and a damage boost for your base AD as well as a 50% bonus for each crit. This is a good choice if the other team is well balanced and the teams are about even.

The Bloodthirster: This is more for the increased life steal because the crit chance and bonus from Infinity Edge will increase your damage more than the 20 extra AD you get from a maxed Bloothirster. For the second build there are much better choices than a fourth Bloodthirster so I would not recommend this for the second build

Guardian Angel: I prefer this with the second build because it protects your Bloodthirster stacks, but it is a viable option for both builds. If you are carrying your team and cannot afford to loose your stacks then I would recommend this item for item 6

Warmog's Armor: I rarely use this but it can be a very helpful item when the other team has a lot of CC and you need those extra 2 or 3 seconds to survive. A lot of people would argue that you need Frozen Mallet and it does combine and bunch of factors that Master Yi needs, but in a much weaker form as alternatives. Its not up to me whether you use Frozen Mallet but personally I don't like it.

This skill sequence focuses on maxing Wuju Style followed with Alpha Strike. This is not something that you should follow every time, but in most cases Meditate is useless and is a bad option compared to other skills. The only time I would recommend getting Meditate would be if you are playing against Karthus (to counter his ult) or if you are getting harassed and forced to back often.

I prefer the Flash/Exhaust combination because I personally dislike Ignite which is the only other really viable option. For those of you who think you should use Ghost instead of Exhaust, you already have Ghost (Highlander) and Exhaust helps confirm early game kills as well as stopping those late game escapes.

Its good to lane with someone who is somewhat ranged and preferably has CC but these are not necessary, but you cannot be as aggressive with these. If you lane with someone who has CC then you can easily get First Blood. I like to stay in lane as long as possible until I am forced to go back, unless I have enough to get both Beserker's Greaves and both Vampric Scepters. I usually go back as soon as I get enough for both Scepters because it allows you to stay in lane longer. I usually don't leave my lane unless I see an opportunity to gank mid or jungle a little before returning to my lane. If you can kill one or both of the champions in your lane then be aggressive and be sure to farm as much as possible, but if you are against a really bad match and your team won't switch lanes with you then play defensively and turret hug. Make sure to last hit to keep your farm up so even if you cannot get kills you don't get to far behind in items.

Once you get your ult usually you can 1v1 any caster or somewhat squishy champion and if you're doing well you should have destroyed the first tower, which allows you to gank or help push other towers. I wouldn't go out by yourself quite yet because at this point you are very squishy and most likely don't have your Bloodthirsters yet. If you're not doing well then turret hug and try to farm as much as possible from the minions so you can keep up late game.

Late game this build is unstoppable against most champions 1v1. This is usually when I start looking for people trying to push lanes by themselves and start jungling whenever I get the chance. When you get to item 5 and have max stacks on your Bloodthirsters you can solo Baron with either build. You will not be much help during team fights, however you can go in and focus the squishys after your team engages. You should also be looking for any lanes with minions pushing it whether its your lane being pushed or theirs. If it's yours then go farm the mob of minions and build up your farm. If it's their lane then go try to push the tower because Master Yi can easily take out a tower if left unprotected. I try to push towers and backdoor every chance I get especially if my team can handle team fights without me, and can keep the other team distracted while I take out a few turrets or inhibs

Once again sorry the build is a bit rough and any criticism is welcome but please at least try it before dismissing it.

If you want to talk to me ingame my ign is LastDarkness, so feel free to add me if you want to discuss something.