Level 11 Rangers
There are quite a few all archer maps that are played on Battle.net, such as Lazer Tag, and archer friends. Alot of these maps have it so archers build instantly, as well as their upgades. The upgrades is where it gets interesting. If you click really fast (using the hotkey is fastest), you can get multiple upgrades of the same thing. So far I've only gotten this to work with the 4 ranger related upgrades. Those being, upgrade to ranger, scouting, further range, and the ranger extra damage upgrade.
As you can see from the screenshot, not even the multiple damage upgrade had any extra effect on my archer. He's the same as he is back at level 7. You can get all sorts of people calling you a hacker by doing this. It doesn't really serve much purpose except for a little bit of a scare factor. This does not work in a single player game, so it is obviously caused by a games latency. If you get a really laggy game, I bet you could bring your levels up even higher. But again, I don't think it would help your archers statistics any.
Thanks goes to Meda_Bot for this information.