After some thought, I had to choose 'shared office'. I have three solid walls around my work space and it feels like an office, but I don't have a door--it's just wide open and I share that part of my space with the fax machine, the copier, the water cooler, a storage cabinet and the microwave. There's plenty of traffic minute by minute and lots of gossip-talk while people refresh themselves with food and drink.
I'm also the first person that people see when they walk into our office area, so I tend to be the one that gets to sign for deliveries, answer stupid questions and direct traffic. I've learned to not make eye-contact with anyone, and I'm getting better at being able to immerse myself in my programming and ignore the hustle and bustle. Sometimes my director will ask me something like "Did Fred stop by to fix the fax machine?" and I can honestly answer "I have no idea. I didn't see him but that doesn't mean he wasn't here." I pay a price for that kind of concentration, though, because I'm often edgy and exhausted at the end of the day just from keeping my guard up.
For security purposes, I do have cabinets and drawers that lock and the office does have a nice window that I can open. I'm on the fourth floor and there are no screens on the window. That leaves me a nice possible exit route if things ever seriously drive me over the edge and I want to end it all.