He's not the best conventional ganker... but if you get creative, he's actually pretty awesome. For instance... great, he has no gap closers, so he's a terrible ganker, right? Not true. Perform a gank from in-lane by sneaking into the enemy's side bush in bottom/top lane, allow the enemy to push hard while you're stealthed, proceed to gank from behind. It's not the fastest ganking method in the world, but it's also unexpected and gets around wards quite nicely.

Also, by maxing his W over his Q, you can actually close gaps very quickly. Frozen Mallet will also help with slows. I guess he's a bit like AP Shaco when it comes to ganks.

Jungle temmo is maby possible if you have a full rune set. Also stated above the wait for enemy at buff is so nice espicaly if you have the sourounding area densley populated with mushrooms.

I am willing to bet that, out of all of you that says it is unviable, none of you have never tried it. So can you please stop theorycrafting?

It works. In fact, it works pretty damn well if you know what you're doing.

You clear jungle fast. You barely take any damage since you can kite in between autos and have a blind against the big creeps.
Against counter jungling, you have a blind and Exhaust. Yes, you take Exhaust.
With just level 1 Blind, you **** any auto-jungler for 4 seconds that comes into your jungle. Not to mention mushrooms to prevent invasions after level 6

In ganks, you're faster than other junglers and can apply red from afar.
For the idiot that keeps talking about Nidalee, she is nowhere as fast out of Cougar form, even if she is constantly in brush. And in Cougar form, she is melee.
Furthermore, she deals nowhere as much damage as Teemo does unless she is in, again, Courgar form.

Lastly, Nidalee traps are visible and provide 0 vision after you lay one down. They are NOT wards. At the very best, you pray to everything holy that they step into it when they walk into a bush. Otherwise, they are just minor inconveniences that you need to walk two steps away from.
Are you seriously comparing Nidalee traps to Teemo mushrooms? Really?

You know what is holding Teemo back? A lane. You can't lay shrooms everywhere if you're stuck in a lane. You know what solves that problem? Not being in a lane.

So seriously. Stop theorycrafting. If you're not going to give it a chance, then shut up.