@All you evil Teemo mains

The SlowMo/Blue build is actually insanely fun and decent

~ ~ choose between these two if you want more damage or attackspeed/chasing potential

Rune set up: http://prntscr.com/il6zro

Your autos permaslow allowing for you to chase endlessly with no hope of them ever escaping while making you damn near impossible to catch due to them being incredibly slow and you being incredibly fast.

Mallet - Mainly for autos and the hp

Rylias - You get this as well because of shrooms plus it fits the theme

Hextech GLP-800 - Again, fits the theme as well as having a pretty nice active since you can shoot it to incoming people rather than turning to auto

Boots - I just go with merc treads since you're already so tanky but either ionia or sorc work (have to be blue so no tabi)

Gauntlet - Slows and makes you tankier, plus it's blue!

Phantom/Liandrys - Liandrys is just a staple in nearly every Teemo build. If you want the damage go for it, if you feel you're ahead enough or just want to be even more annoying then go for phantom dancer, more autos, more tank, more speed to keep slowing. Up to you.

May not sound like a good build but try it out in a game and you'll feel disgusted as well as very satisfied. (I had the luxury of bullying a Riven and boy do they deserve it)