I'm a developer in Pittsburgh who works on various opensource/free projects in my free time (in addition to my daily job) -- The project I mostly focus on right now is Xonotic, with which I am one of the core developers and contribute most of my free time to.
Seems very plain, lacks any really engaging gameplay... and it generally lacks content in the first place... eh...
Great project, very polished... I personally just dislike the gunplay, I don't think it feels solid enough..... the weapons feel unfinished or rather just unsatisfying to fire. But considering it is early, I still find it very fun, and enjoy playing it from time to time.