Since the new Teemo update i kept this build as a little secret to myself but i decided to share.

Not sure if anyone has posted anything similar so if they have forgive me =]
You are welcome to post any advice or criticisms.

This build usually works with any support since the damage output is insane. I prefer Blitz/Nunu + Teemo.

This build requires you go get a Guinsoo Rageblade as soon as possible.

Flat AD reds
Armor Yellows
Flat MR/MR per level blue

1. Boots+ Pots[/B]

2.Rush Guinsoo Rageblade then Vamp Sceptre (You can get Blasting Wand/Pick Axe depending on your personal preference, I usually get blasting Wand for extra shroom and blind damage).

The reason for Guinsoo's is because of his E. The on hit AP ratio is now 0.4. At Max stacks Teemo receives around 94 AP from Guinsoos increasing the on hit damage to 87ish at MAX Level E. It also increases the DOT damage as well.

Assuming you are lvl 6 you have 24+37(Toxic Shot on hit dmg, not including the DOT and Guinsoo @ 8 stacks) + 35 (Guinsoo AD)= +96dmg per hit. Which is insane for a 2.3k item. The added attack speed also gives you a huge advantage in lane.

3.Zeal -> Phantom Dancer
Mad AS/MS + Crits.
(Sometimes i keep zeal and rush Madred's BloodRazer first. I purchase Recurve Bow for the lost attack speed first and then proceed to finish Madred's).

4. Madreds BloodRazer/ IE
Up to you which one you want to get first, you'll want to get both. I usually like getting Madreds first but IE should be just as good. The AS from Madreds and %life Damage makes your damage go through the roof. Once you get PD and Madreds your attack speed is around 2.1/2.3 depending on whether you have max stacks on Guinsoo's.
With Nunu you get 2.5(MAX AS)

5. So at the moment you should have...
Berzerker's Boots, Guinsoo's, PD, Vamp Scepter, Madred's,IE. This is where the problem starts. Usually the game ends before i am able to get a GA but if it get's to this point i usually get rid of my Vamp Scepter for a GA and then swap the Guinsoo's for a BT.

1 point on QWE at early levels. Level up and max E first.
Max Q second (Since you have a Guinsoo's).
Point in R when you can and max W last.

I usually bring flash and ignite.

Ignite works well with the poison and flash needs no explanation.

Play Style:

Here i'm going to talk about play style, with the assumption that your support is Blitzcrank. I know what you're thinking, Blitzcrank? WTF? I thought that too but providing you have a good blitz(i.e a blitz that can hook) you'll win trades 100% of the time.

How to use your skills
Like a normal teemo you'll want to blind their AD carry AFTER they use their damage spells. However you can also use the blind to harass. Since you'll be maxing it second and you have guinsoo's, your damage on your Q will be quite high. Just don't spam it out in lane because you'll need it for when your support decides to engage.

Harassing and Pushing
You'll be playing as a POKE LANE
Teemo's main power is his harass, you don't want to go too aggressive but you don't want to be too passive, so try to harass when you can, try to bully the enemy AD without losing minions.

You'll also want to push your lane if you can so you always have the bush under your control, not having bush control is hell for Teemo, especially if they have a Taric or Leona. Just make sure your Support wards so you know when the jungler is coming.

If you are against a kill lane, just play passive and wait till your Blitz hooks. Then go all out and rape them. If you don't successfully get a kill then shame on you!

Shroom Placement
Once you get to level 6, this is when it starts getting fun.
Your shroom's should deal a decent amount of damage if you have max stacks on Guinsoo's (which you should have most of the time from pushing).

Place your shrooms at the beginning and end of the lane bushes and also on either side of the lane so that they don't get triggered by minions. You should also place some behind you so if you get jumped you have an escape plan ready.

Because of this shroom placement shrooms usually get triggered when the enemy support walks into the bush/ or walk on the side of the lane, which means easy pickings for your blitzcrank. Once they get pulled it's all over for them.

If your blitz is good you can get him to pull the enemy into the bush and onto the shroom. Which is hilarious.

Being pushed back early in Lane
In the case that you're getting pushed back at lane, never fear, just last hit at tower, teemo's E makes it super easy for him to farm at tower. Once you get your Rageblade it's all over for the enemy AD.

Team Fights
The worst thing about Teemo is that he doesn't have any escape abilities.
What you'll want to do it stay at the back and hit who ever is closest and try not to get burst down by the AP carry and remember to use your blind effectively.

Another reason i get Madred's before is that it helps kill bruisers really quickly because of the increase in AS and %life damage. So you won't spend ages trying to kill a tank.