"Name That Extra Room" Contest

I received word yesterday that my potential roommate is a no-go, leaving me with an entirely vacant bedroom. At the moment, I am using it to finish unpacking and sorting my remaining boxes -- but then I am faced with a dilemma: to look for a roommate or not to look for a roommate?

If I don't find a roommate, what do I do with the extra space? My office/sitting room is so far working out very well, and I already have more space in my kitchen, bedroom and living room than I've ever had. What's a girl to do?

Some ideas I've thought of:

1. Move my office to the spare room. There's more light, more space, and I would never have to worry about the neatness of my workspace in the rare event of guests. 
2. Create a dedicated guest room. I like the idea of a spare bedroom for guests, and could even have it available for short-term rentals or visiting students/scholars/faculty.
3. Work out/yoga room. If I had an entire room dedicated to exercise, am I likely to do it more? 
4. Some other combination of uses I haven't thought of yet?

Post your suggestions and daydreams for me here!