So, I'm back with another hero and another build, I've been playing Master Yi for about two weeks now, so I know that doesn't make me an expert, but I've been playing with a very good friend of mine who used to play Master Yi. Basically I started off with a very odd build and decided to try a hybrid build, as I was developing the hybrid build I found it works great for a Jungle of sorts. You will be in and out of the jungle like -snaps- that because of your attack and movement speed. You will perform many ganks, and if you get gold fast enough you will be able to take out dragon pretty early.

Well, I like this rune set because theoretically it works great. I do not currently use runes b/c I can't buy them because I am still trying to choose which hero to use. So here is my choice:
9 reds of critical damage to get you to be a damage dealer quick.
9 yellows of Dodge because you don't get a whole lot of armor so the more chance you have not to get hit, the better.
9 Ability Power per level blues because it's important that you get your AP up to heal yourself and deal damage with your Alpha Strike
Quints of AP per level so that you basically get a lot of AP early on and late game.

Alright, I choose a 29/1/0 build because you are an aggressive champion and the point in defense helps your Smite summoner spell.

I can't get all of these because I am not lvl 30 yet, only 25. So this mastery set is what I am building up to. I'm sure once I get level 30 and can experiment a bit more than I will edit this.

Alright now to the bulk of the build:
I start off with a Meki Pendant because you need mana regeneration to cast your Alpha Strike and Meditate often enough to stay jungling for a long time without the need for potions.
I move on to make a Tear of the Goddess because it is like an enhanced version of the Meki Pendant. The longer you can stay jungling and ganking the more of a chance your team will eb successful.
The basic Boots comes up next because I hate going slow and the faster you can move without your ultimate the more of a chance of successful gank and jungling counter escape.
Archangel's Staff is next because it is going to build up your mana, mana regeneration, and Ability Power.
Zeal comes next because by now you need more movement speed and attack spped to jungle effectively. The critical strike also helps getting those big hits.
Your next two items are used to make the hextex gunblade this is mainly for that bit of life steal and the AP bonus you get. The added perk is the unique passive of spell vamp which stacks great with your Alpha Strike.
Now you need to upgrade that Zeal into a Phantom Dancer this item is basically a buffed Zeal for more Move Speed, Atk Speed, and crit chance.
We move now to the Infinity Edge this is great for Attack Damage and crit chance, you will be able to take out just about any now uber tank fairly easily so long as they don't have like 6 stuns...
Executioner's Calling this was mainly for the added life steal, but the crit chance is going to push you right up to almost 100%
I finish off with a Phantom Dancer because I enjoy the move and attack speed along with the crit chance now pushing you over 100%. This is wthe item you sell your regular boots for.

So as a jungler you will need your Alpha Strike to quickly take out the spawns, but it also gives you the ability to go farm lanes very quickly being able to jump in and take out an entire mob with one move is pretty good.
Meditate is important to get second so that you don't have to waste gold on potions necessarily. Your build is already going to cost near 20k to make so why spend more?
Wuju Style I don't get this until level three because you don't need it until then, by level three you should be going for the buffs, and the added attack damage is great for getting those buffs easily.

Teleport is used to get in lanes when your team is struggling or needs to recall, it can also get you out of sticky situations if used right.
Smite is obviously because you will be jungling and so the Smite will get you some extra gold and help take out those buff mobs.

You should jungle with this build because it has good sustainability and ganking prowess. You pretty much jungle like you would any AP jungler, you hit blue buff with the help of a 'leash' from a teammate. Blue buff is most helpful on Yi so he can heal often and cast his Alpha Strike in quick succession.

At about level 8, if geared properly(have at least a Hextech Revolver), you can begin attempting dragon by yourself.
At level 6 you should be ganking lanes, focus low health champions and the mid lane champion. jump in on them with your Alpha Strike activate your Wuju Style mid jump and when you start hitting use your Highlander you keep up with them and attack rapidly. Don't chase into the tower unless you only need one or two hits to get them, then get out and use Meditate before you recall to get a bit of health back.

Pretty much just run around the jungle killing creeps as they spawn, be sure to run into lanes and drop an Alpha Strike on unsuspecting minions to rack up gold fast.

Pros:
You hit like a truck
You can heal rapidly and get back into fights without recalling
You are not very prone to death because you are only in lane for short bursts
You can easily take out aggressive enemy champions that push just a little to hard.

Cons:
You are not tanky, you don't have a whole lot of health or armor/magic resistance.
You often are to fast for the jungle on your side alone to re-spawn so you will find yourself often in enemy territory, which can be dangerous, especially if the other team has a jungler.

(Date of edit) reason for edit
(12/14/11) edited mastery page-added a crit damage spot.