pro's
high damage ouput
very good wave clear capabilities

con's
extremely squishy
very low early game capabilities

as i said earlier maxing his toxic shot scales quite well with the item build. 1. toxic shot scales very well with hurricane because each hurricane bolt is on hit affect so each one hits enemy with poison. 2. it also scales very well with Guinsoo's Rageblade. the rageblade gives attk speed with each basic attk which allows teemo to have an edge in a 1v1 fight. also the blade gives both ap and ad dmg output which helps a lot to his toxic shot as well as his hurricane's dmg output, since the hurricane scales off ad. 3. hexteck revolver is also another good skill that scales along with his e passive. also the hexteck gives ad and ap dmg output aswell which scales very well with his hurricane aswell. not just only does it give ad and ap and scales with hurricane it gives teemo spellvamp and lifesteal which together stacks with Guinsoo's blade when he drops under 50% hp. 4.the wit's end. wit's end gives a bonus dmg of 42 per basic attk. that also sca;es very well with teemo and his hurricane. also gives em mr per hit and more attk speed. 5. rabadon's. the rabadons scales very good with teemos shrooms and his q. it gives you that high ap dmg output to provide more dmg for your toxic shot to deal more posion dmg overtime for the kill while the enemy decides to run, saves you the trouble of not having to chase and get ganked in process of the chase.

i usually run flash and ignite on teemo. ignite is very good to get that final bit of dmg to finish off your apponent to prevent yourself from getting killed or if your about to get killed and want to kill the enemy along with you. also ignite helps very much against champions who use shield skills such as lulu, diana, lux, etc. flash allowes you to get away from heavy ganks along with your w's extra speed boots. barrier is also another good options because it gives you that extra bar to take a few more hits in a teamfight. also if your more of a team player you can run teleport. is quite affective on teemo as he can get back to lane phase much faster than most champions right after winning a teamfight, or from killing dragon.

runes can be used in many different ways but, i mostly prefer a well balanced rune build. i use MP marks for the extra magic pen for his skills and on hit e passive. i run armor seals to help me with ad junglers who attempt a gank on me, allowes me to take a few more extra hits in order to get away safely. also the armor seals help if your laning in bot lane. the mr glyphs help me have some sustaint along with wits end against ap champions wether im being ganked or laning mid. and the ap quints gives me that tiny bit of an edge to be able to one last hit minions in lane with my e passive on hit affects, also allowes me to give a tad poke every now and then.