My first build!! I made this build because I see a lot of Yi players who completely play him wrong; Spell order, items, etc.. I'm not trying to say that my build is the best out there, but I find it VERY, VERY effecrive. I can hit tanks like Singed and Blitzcrank to death within a few seconds (except when they have thornmail or if it is rammus....). Most carries go with 2 or 3 hits.

The goal of this build is:
-Reaching maximum speed while not focusing on it.
-Ultimate damage
-Getting critical damage
-Outrun ghosters and escapers
-To win.

I would like to keep short about the runes. ArPen marks and quints, as it nicely stacks with your Ghostblade, and get you even more damage. Can be swapped for crit dmg. Dodge seals, I like them some way, but can also be swapped for armor or magic resist, as Yi is a very squishy champion. CDR glyphs, can be swapped for most things, but I find it effective.

Pretty obvious 21/0/9 masteries, Getting ArPen and Crit dmg in Offense, less time spend dead in Utility (why? BECAUSE YOU HAVE TO WAIT A ****LOAD TIME WHEN YOU DIE) and some gold gain, can be swapped for the buff duration. 9/21/0 masteries could also work to counter his aspect of being squishy.

The item build is VERY important. Do NOT change it ingame except when REALLY needed.
Obivous choice for my beging game: I take boots+pots at start. Go back when you can buy your Greaves+Avarice blade. Get Ghostblade after the Greaves. Now you may think: Excecutinors Calling? For Yi? Why? JUST BECAUSE I LIKE IT!! It gives crit and lifesteal for a very good price, so I think it's really worth it. Grab a PD, Infinity Edge, a Bloddthirster and then another Infinity edge OR a Bloodthirster.

I like to get alpha strike at lvl 1, as it's better for harassing and farming. Get your Wuju style at lvl 2, and only activate it when you need some extra damage to get a kill. Max your Wuju style and Alpha strike and level your ultimate whenever you can.

Now I will show you why I have chosen this.

Why use this? Good question. I found out that Crit Yi is just the most OP thing in the game. It defeats all other OP champs such as Tryndamere, Evelynn, Nocturne, etc. It knocks Carries, Mages and supports in 2-3 hits. Tanks go in a few seconds. How? That's very easy.

Yi is able to reach the BEST speed in the whole ******* game without having to focus his build on it. Ghostblade and PD, the rest is all work of his Highlander. 2.5 attacks per seconds, all 700-1000 dmg crits (this is the practical damage, not theory.), with AMAZING speed, it's better to fight Yi then to run away: Either way you lose.

**THE ORDER OF SKILLS YOU USE IS VERY IMPORTANT**
Just to clear something up: With 2 I mean your Ghostblade, as it will be in your second slot, and the hotkey will be 2.

It's very easy:
2>E>R>Q.
How easy!
YET.
IT.
IS.
VERY.
IMPORTANT.
NOT.
TO.
DO.
IT.
ELSEWAY.

If you use your Q first, you will save 1 second from your ultimate and ghostblade, but you'll have to hit 3 buttons before you can focus your very first target. And that is where Yi dies.

Yi is very, VERY squishy. He depends on lifesteal, which makes him very vurnerable to CC. Thank the lord he gave us somehting: NO SLOWING DOWN. Ever tried to hit an Ashe which has 3 PD's with a Gangplank? Pretty impossible, aye? That is where Yi comes in. Let us make that a little scene:

Fed Ashe: HAHAHA who wants some frozen arrows on his ***?!!?!?!?!?
Yi: 2>E>R *runs to ashe with unmatched speed*
Ashe: OH GOD I NEED TO SLOW HIM!!
CAN'T BE SLOWED?! WHAT IS THIS?!
Yi: *2 shot ashe*
Ashe: *ragequit*

Most non-tank champs go down with some 1000 dmg crits. That's the way for me.

Pros:
-Amazing farmer
-GODLIKE Damage
-LEGENDARY Speed
-Fun to play
-Not so pricey as he is nicely OP
-Counters any other AD character

Cons:
-VERY Squishy
-Needs to be fed well if he wants to shine
-Vurnerable to CC
-Oftenly misunderstood

My first build, I'll probably have to improve it some times, make it bigger, etc, but I am glad I could share this. Please Rate/Comment, and let me know what you think.