Dark room in the basement or bright room with large windows?
It depends on the season. During the Winter it definitely feels like a basement as it's so dark all the time even though there's a large window behind me. The Summer can be quite bright so you get entirely different vibe.
There's some kind of a productivity difference too. Winters are mentally harder due to the darkness.
Fancy table and chair combination or some old pieces gathered from friends?
The furniture is quite old. Wooden table (custom corner for extra working space), comfy chair. The chair might use an upgrade.
I bought an Easel laptop stand to help with ergonomics. It helps a ton to have your wrists in a slight angle. If you are on a budget, consider doing something ad hoc yourself. It's a little thing, but once you get used to it, it's hard to live without.
Are you coding on a crazy old machine, you wonder why it's still alive or is it a shiny new gem?
I use a Mid-2012 13" MBA. It's still a decent machine although I would like to update to something more modern once Apple gets new models out there. My biggest gripes with the current machine are the tiny HD and poor graphics performance. I could also use a retina display.
What tools to you use?
I tend to spend a lot of time in Sublime and vim. I use a split display setup. I have eight iTerms open always split to left/right. I autojump around to set the context right. Editor is always on one half or both.
The setup is simple but I like it as it allows me to use my limited bash-fu and terminal commands while having a good editor available if I need it. I handle git operations through terminal for instance. I tried the Sublime plugin but never could get used to it.
Chrome is my workhorse when it comes to browsers. It has solid development tooling included and it keeps on improving solidly. Perhaps it might be cool to try something alternative like Vivaldi, though.