Master Yi is a fast char that can diliver great amount of damage in short period of time. He is one of the greatest (if not the best) carry/pusher/farmer ingame.
Apart of great dps, huge criticals, great atack speed he has a superb chasing mechanism as well as it can be used as superb escape mechanism.- After all he is a Master :)

The runes i made them for ganking Dmg attack speed and crit are needed for him so he can get alot kills you can also try to do ARP runes

Alpha Strike (mana cost: 90/105/120/135/150): Master Yi leaps across the battlefield striking up to 4 enemies, dealing 100/150/200/250/300 (+AP x 1.01) Magic Damage and has a 20/30/40/50/60% chance to deal 400 bonus damage to minions. 18 sec. cooldown.(Master Yi's early farming ability/harassing ability, I Use this on minions when ever enemy champions are near them, it's great for harassing and the enemy, most of the time, the enemy won't be quick enough to react and hit you as you run back to your minions.)

Meditate (mana cost: 80/100/120/140/160): Master Yi meditates restoring 150/300/500/750/1100 (+AP x 1.65) Health over 5 seconds. While Meditating Master Yi has a bonus 30 Armor and Magic Resist. 45 sec. cooldown. (Great ability late game as it restores about 60% of your hp. It also scales pretty well with ability power but stacking ability power is not needed to make use of this ability.)

Wuju Style (mana cost: 40): Passively increases Physical damage by 15/20/25/30/35. Additionally, Master Yi can activate this ability to double its effectiveness for 10 seconds, this removes its passive bonus damage until Wuju Style becomes available again. 30 sec. cooldown. (This is Master Yi's main ability it works hand in hand with highlander for pushing towers or owning champions. Always use this when attacking Towers as you are a great tower destroyer. Don't waste this on minions try to keep it off cooldown unless your ganking or smashing towers.)

Highlander (mana cost: 120): Increases Master Yi's Movement Speed by 40% and Attack Speed by 30/50/70%, and he becomes immune to all slowing effects for 6/9/12 seconds. Additionally, killing a champion refreshes all of Master Yi's cooldowns. 70 sec. cooldown. (Great for champion killing and tower pushing, pop this with Wuju Style and you'll have that champion/tower down in no time. If you kill a champion with this popped it will refresh all your cooldowns, including Highlander! Make sure that you don’t pop Wuju style until the old one runs off because it will stack with your popped one [I.E level 5 Wuju Style= 35x2 while it's active +35 of your passive =105 physical damage!])

Double Strike (passive): Master Yi has a chance to strike twice each time he attacks. (This works great with the Razors as you can hit 500's twice!)

Yi Solo Mid - How To?

ALWAYS start off with Boots of Speed, 2xHealh Potion, 1x Mana Potion.
Put your 1st point in Wuju Style.
Head for mid lane to check who are you laning against.
If it is Heimer, and he planted his 1st turret down, kill it with activating Wuju style, port back to base and replenish hp+mana before creep spawn start. If it is Teemo try to force him moving and not beeing able to stealth in middle of the field.
If you face other chars, just hug your tower untill mobs come.
1st lvl is boring. Try to stand back and only last hit creeps for cash. You can try to force your opponent to spend mana, health pots, heal spell by hitting you. You have 2 hp pots to replenish hp anyway, dont hesitate to use em.
On lvl 2 take Alpha strike. This is the part where fun begins. Stack up your double strike untill you get "Your next strike will be double strike" buff. Let your opponent push a bit, you can try porting to base trick to lure them. When you feel you have enaugh space to chase and kill do:
Enable Wuju Style, Alpha strike targeting your enemy (so you will land on his location as last strike) Pop Exhaust and get a free kill. Heal is not enaugh to survive your attack but keep in mind what summoner skills does your enemy have. If it is flash be ready to flash with him/her to continue hitting.
If your opponent is tough, has high hp pool or armor, try doing same but without exhaust just to harras. than get your double strike ready again, and begin the action this time with exhaust into kill. Repeat untill you feel like it or you destroy the tower. If you see one of the bot/top lanes beeing pushed too much, dont hesitate to go there. You will have alot of space to chase them and evetualy granting you another free kill and a greatefull part of the team :).
On lvl 6 try to port to base to replenish mana/hp, and let your mid opponent push even to tower. Kill him/her with standard AS->WS->HL combo if nessesary flash or exhaust.
While picking items try focusing on getting AS as fast as you can (even buy Vampiric Scepter last in malady parting, than focus getting Zeal and again rush for Dagger 1st.
Why? We want to get those 7th hits landing as often as possible. (best in early game would be landing 2 7th hits in a single Wuju Style activation.

Middle lane champions that you will take with ease:
Ashe, Karthus, Anivia, Ryze, Veigar, Shaco, Sivir, Twitch, Janna, Swain

Medium Hard:]
Amumu (stun, tank), Annie (stun), Corkie (valkirie), Ezreal (Arcane shift), Fiddle (fear), Katarina (shunpo), Kennen (lightning rush), Nildae (pounce), Tristana (rocket jump), Twisted Fate (stun), Zilean (time warp), Morgana (dark binding), Lux (binding).

HARD:
Heimerdinger (Stun, blind, turrets, long range, passive playstyle), Teemo (blind, high damage, mushrooms), Kassadin (Riftwalk, silence, good damage), Sion (2sec stun, BIG DAMAGE, tough (passive), high hp), Malzahar.

I am still trying to get better on those hard champions, any1 that has some tricks i could try post :)

Master Yi is a great farmer. This is good, since you’re going to spend most of the game farming to get the gear you need to do well=D. To accomplish this you’re going to depend on timing Alpha Strike to last hit minion mobs. You can also pop Wuju Style to up your dps long enough to take out a minion mob.

Early on, you’re going to want to sit back and wait for the minions to come to a position where you can safely Alpha Strike them. You don’t want to Alpha Strike and end up in the middle of 2 enemies. Early on you’re too soft and they’ll end up pwning you. If you’re laning against 2 enemies who are trying to harass, stay back and wait for the minions to come just out of the range of your tower.

When they get in range, Alpha Strike and you’ll kill most of them. You can kill the remaining minions with your normal attack by juking back and forth until the tower gets them low. If you’re close to your tower and there are 2-3 minions and an enemy around, you can use those minions to slingshot into the enemies with Alpha Strike. You’ll damage them and land safely behind your tower.

Before I do any jungling, I like to wait until at least lvs 2-3. Jungling is very difficult without at least a second rank in Alpha Strike. The first camp you want to hit is the one with the specters. Alpha Strike them and if any are still alive, pop WuJu Style to finish them off.

If you want to focus exclusively on jungling, then you’ll want to pick up Madred’s Razoras one of your first items. Madred’s allows you take out the golem/lizard earlier, but I almost always skip on this item since I can plow minions so easily with Yi in lane. The money I save on Madred’s allows me to funnel gold into Zeal, Chalice, or a Vamperic Scepter. I often stick mostly to the lanes, but if I have 20-30 seconds while I’m waiting for more minions I sometimes hit a few minion camps to pass the time.

Play Video

Pros and Cons by me
Pros:
1.Really strong
2.Great abilities
3.Ganker
Cons:
1.Bad vs tanks or like theese charecters
Heimerdinger (Stun, blind, turrets, long range, passive playstyle), Teemo (blind, high damage, mushrooms), Kassadin (Riftwalk, silence, good damage), Sion (2sec stun, BIG DAMAGE, tough (passive), high hp), Malzahar.

34/2/2 :D once 2 deaths only on 4v1 XD