Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
I have been using this build since i started teemo, and at times he can get up to 425-470 dmg at end game.
between Malady, Blood Thirster, Black cleaver and your Poison you should be constantly doing dmg and heavy dmg at that. But he isnt an initiator he is a finisher, let one person initiate then run in and finish them, you might ks but you will take them down fast. My last game i was doing ~300 dmg to inhibitors and ~200 to turrets per shot. my AS is ~1.8 end game. Most people use him for his AP builds but this build takes advantage of his naturally high AS, and constantly use his shrooms because you wont need the mana for anything else, and his blinding shot i only use to get away so that they miss while AA and I dont get knocked out of his run. This is a steer away for some people but i think those who never really found a liking for him will like this build. Late game is where he really shines, because by that time you should have mushrooms all over to either lead into or to tele to. His AS isnt as important as his AD, and with his poison it just adds that extra sting to the kill. This build also carries a team, especially if you are behind and you can find those few good ganks, then you can gain that edge and take the game back. I cant count how many times i have brought my team back from what we though was a loss... All our turrets outside our base were gone and only had maybe 1 or 2 of theirs down. With in 5 min we turned the tides and won the game. He does perfect in mid, just remember to flood the sides of mid with shrooms to prevent a gank and to give you an out if needed, once you push through mid then tele to top or bot and lay shrooms for outs for your allies.
This is my first build guide so there might be flaws or somethings i can work on but i have been quite successful with this guide.