In the ever-expanding and competitive realm of MMORPGs, Knights Online has a sturdy reputation for offering the most for free. A heavily-populated game, with nearly 300,000 people online when we played, Knights provides a familiar fight-and-quest medieval milieu that encourages interaction with other players but doesn't demand it.
For a free download, the graphics are top-rate. As you acquire weapons and armor, your character's physical appearance changes to reflect both the new implement of death being swung and the new pants you're wearing. The POV changes are fairly smooth and occasionally disorienting for it. There also is a paid upgrade version that opens up a community that allows you to sell items at a higher rate and more power.
The user subscription has another benefit: consistent access. The game is so popular that free players are blocked during peak hours. There are the usual drawbacks of cheaters and complaints about customer support, but the biggest problem we encountered was the installation. On top of the massive install file, we were required to add 13 patches with absolutely no documentation; it was only from the Web site's player forums that we learned about them.
All that being said, it's a fun game that can magically obliterate your free time--and leave you happier for it.