Adventure Quest. The worst implementation of an online game I have ever seen. On its defense, it fufills its role as a lunch hour sized RPG. Leveling up is easy and there is a nearly ridiculous amount of armor, weapons, and pets.
The down side is you'll never experience that. Because "free web-based RPG" doesn't tell you that the servers are full of paying members. Unfortunelately, the paying members don't use their server enough and are counted in the "players online" count.
So you'll never play unless you fork over 15$ for a supposedly free online game. And that's just a rip off. Also, leveling up is easy and fast, but the monsters the throw at you get stronger faster than you do. If you're level 10, odds are you'll be fighting level 16 monsters. These aren't the easy to kill NPCs in most RPGs. They will kill you. Easily.
So, I'm asking all of you not to play Adventure Quest. Save your time.