I pretty much just randomly came up with this build by improvising.
Since it's nearly 5am, I'll make this quick:
Doran's Ring > Warmogs > Boots of Swiftness/Berserker Greaves > Atma's impaler > Frozen Mallet > Infinity Edge > 2 Phantom Dancers
Dorans ring helps when laning a LOT. As long as you learn Meditate at level 3 or 4, you'll be fine.
Warmogs works very well with Yi, as he is a brilliant farmer, yet will be almost indestructible. Just to abuse that ton of HP you have, why not add insult to injury?
Atma's impaler will give your decent amount of attack damage - certainly enough what your current level.
Frozen mallet speaks for itself - Attack damage, a great unique passive and all that HP, which add perfectly to your stockpile of AD.
Now to bring in the pain - BRING IN THE INFINITY EDGE!! This speaks for itself!!
Just to finish things off, sell your Dorans ring and boots of swiftness/Berserker Greaves and add two Phantom Dancers! Since the Phantom dancer provides 15% speed of its own, you won't have to rely on those grubby boots any more.
Crit Chance without masteries/runes = 98% (Atma's - 18%, Infinity Edge - 20%, Phantom Dancers - 30% each)
Crit chances with 21/9/0, yet no runes would be 100%
I've never fully completed the build, due to the lack of time given (enemies surrendering), but I know it would be absolutely perfect.
Yi would have about 3600-4100HP (You'd get about 80AD from Atma's impaler)
Frozen Mallet adds a fair share of AD.
Infinity edge adds a LOT of AD
Phantom Dancers add on the DPS.
So guys, what do you reckon? I've only used my build twice, but it's been successful both times.
Another reason why this build is pretty effective, is that it enables Yi to tank turrets by himself, meaning he can be destroying enemy turrets while the enemies are at your Inhibitors. (I recommend Teleport and Ghost for this to work efficiently).
Here's a printscreen of both the games: