What is the best free fps game?

QuakeOnline.

End of thread.

Wolfenstein: Enemy Territory, a free multiplayer FPS built off the Return to Castle Wolfenstein.
Sauerbraten is another good one.
Both have dated graphics, but I guess you get what you pay for.

@PapaLeo QuakeOnline is free?

Yup.

Other than the time you invest, of course.

@PapaLeo So, you don’t need to purchase any software or anything? How do you play, just log on to their servers?

That’s right. I couldn’t believe it either. I have no idea what their business model is, but I like it.

Not only that but it’s absolutely superior interface: automatic placing in level per skill, mutiple maps and great communities. If I got a letter in the mail tomorrow asking me to pay €50 to keep playing for free, I’d pay it readily.

Oh . . . wait.

There is also the excellent but (compared to Source and other games) scarcely played Warsaw. It is similar to Quake.