I run the MMO A Tale in the Desert. We charge $13.95/month for the game, and pay about $0.74 in merchant and gateway fees.

We'll now accept Bitcoins as an alternate payment method. The price per month is 2000 BTC, which according to the exchange is a discount right now.

Instructions:
Visit http://www.atitd.com and download the game client. Native Windows, Linux and OSX versions are available.
Install + Run the client, and create a trial character.
If you like the game, send 2000 BTC to: 17CJvRrNdqSPN3Zs2dWfNY6GoCiMRfNG2T to activate your account.
In the message field, include your character name and shard; I'll then credit you for a month of gameplay.
Right now this is done manually, so the lag could be anywhere from minutes to the next morning.

Teppy