Ahem...
Helloooo! :D I'm NotJarrod. For the longest time I've loved Teemo and I've played him since the beginning of my League career. I've gotten my highest scores with him (something like 34/2) and he's by far my best character (even if he's not my most favored).

This is my first build, so please don't be too harsh on it. Also note that this build didn't take much time and will have more effort put into it later.

I tried to pick out some items that would make Teemo as much of a nuisance as possible, because this build is mainly built around your shrooms. This build is especially good against those pesky, squishy AD carries such as Ashe or Ezreal. This also works with tanks, on the other hand. Tanks, unless it's Galio, aren't going to stack magic resist just to defend themselves from you. So you're still going to do some pretty good damage against them. And you always help a bit in chases because of your Rylai's slow. Another reason to follow this build is because you frequently pick off random kills from people who are running away from a team fight on low health, or just running into shroom after shroom! Anyway, lets get down to the build.

Don't get your skills right when you start wait until you see what you're laning against (get Blinding Dart if you're against an AD carry, get Toxic Shot otherwise). I always get those 2 skills first and then get Move Quick third. Level Toxic Shot whenever possible until you max it. When you can't, get Blinding Dart. Then do the same thing for Blinding Dart. And then max Move Quick. And of course, get your ult whenever possible. It's the most important part of this guide!

My runes may not be the best, but it's what I use all the time and it works perfectly fine.

AP runes: As I said, this build is basically built around your shrooms. They help a lot early (and late) game with your poison and your blinding dart, and they help even more with your shrooms.

MS runes: The reason I have these quints is because they make any character able to run away or catch up to others. Even more so to champs like Yi that are already fast (since it gives bonus MS based off how much you already have). I use it for every champ and I highly recommend it.

Pros:
-Fast
-Effective
-Annoying
-Super cute, annoying, spammable laugh
-SO MANY SKINS!
-So darn cute
-Did I mention he's cute?
-The other team will rage
-People hate you
-KS because of your OP shrooms

Cons:
-Squishy
-Will probably get focused
-The 2 above reasons are enough trouble as it is

Well, I used to play AD Teemo. I liked him a lot, but it got boring for some reason and I really never went back. I started experimenting around 1 game and came up with the build waaaay up there and I actually did good. I've been using it ever since and I love it. I never miss an opportunity to laugh at somebody who doesn't expect my damage to appear out of a bush.

The reason you should pick AP Teem over AD Teemo is the fact that Teemo only has a range of 500, so he has to get in range a bit more than other AD carries. Most champions have a skill about that range and it would only be an exchange, not you harassing them and AP Teemo will make the other team rage a lot more than they would with AD Teemo.

I'm not saying that AD Teemo is a bad choice, because I've done good with him. I played AD Teemo just once recently (first time in almost a year) and I did alright. All I'm saying is that AP Teemo is superior over AD Teemo for a lot of reasons.

I can not say this enough. ALWAYS shroom! You should never have 3 shrooms ready at your disposal. Keep it at a maximum of 2. Now, don't go and die because you want to put a shroom down so much, be reasonable.

Beginning game it's a good idea to block of the mouths of the rivers and behind your turret in case the enemies dive you. Place those shrooms in high traffic areas, such as the entrance to blue and in the tri-bush at your lane.

Mid and late game you should shroom everywhere. Especially around those high traffic areas such as Dragon and Baron. Shroom Dragon more often early game since they won't be going for Baron when they're too weak. Later on, whenever you feel like it's a good time, start shrooming Baron. That's one of the best parts having AP Teemo, let alone Teemo, on your team. You have tons of map awareness, damage just waiting to be detonated, and a fall-back plan for when you're getting your buns handed to you.

Once again I CANNOT stress enough how important it is that you shroom, especially when you use this build. That's all this build is about, shrooming!

Rylai's: Will give a bit of health that you need, a slow, and some AP. Great for your already annoying shrooms and Q.

Nashor's Tooth: Much needed CDR, some more AP, and a good helping of AS. Not to mention it gives some mana per 5 which you will need for spamming shrooms. Great item on Teemo regardless of how you're playing him in my opinion.

Void Staff: AP and magic pen, what else can I say?

Boots: These give you speed, of course, but you need to make a choice. If they have a team with a lot of CC (which they will more likely than not), you go ahead and pick up a pair of Merc Treads. If not, or if they are getting a lot of magic resist, go get Sorc Shoes. It's simple as that.

Rabadon's: Do NOT forget this! It gives a load of AP as it is, but it also gives more based off how much you have. This is perfect because that's exactly what you're going for. I can not stress enough, do NOT forget this!

Athene's Unholy Grail: I always get this because of it's unique passive. I'm always shrooming and often times I run out of mana. Since you're to be shrooming everywhere, you should run into the same problem. So because of that, it pays for itself. For any kills or assists you may get, you get mana. A lot of it too. And you can never forget that it gives you even more AP and a bit of magic resist. 1 more thing, it recently got buffed so it will give more AP and more magic resist than it already does. It's so perfect for this build!

Sorry for any grammar/spelling errors I made in my build. I hope you like it, and don't talk trash about it 'til you try it! Please leave a comment with constructive criticism, things you would like me to know, or a rating. Or all 3! All 3 would be nice... Until next time, keep on shrooming.