I have a standing desk, with a nice tall stool so I can sit when I want. Nice big display off to the side of my laptop, lovely for design work. I tend to keep several sets of desktops open, with related applications running, typically (1) browser with trackers + slack (team! woo!) (2) Browser window with local instance of the app we're working on, for testing, with (3) TextMate + iTerm (4) Illustrator + Finder (for moving the design files where they need to go).
I have a nice whiteboard to make notes to myself or work things out on. There are a number of additional whiteboards around the office that I can use when a larger space is needed. I keep a paper notebook that I use during meetings and to sketch out ideas. There's a wacom tablet under my laptop stand, along with my backup drive. Generally have a bit of a hoard of books and snacks tucked away at the bottom of my desk. I have a handy induction charger for my Nexus 4, terribly convenient because I can just set my phone down and it's charging. I use my phone for testing and to check email etc (I generally don't keep email open on my workstation because I find it to be distracting).
Also notably at the time of this picture taking, my desk is hosting both a banana phone and an actual edible banana. The bananaphone is really just decorative, at this point; it was purchased in a moment of fun/despair at the prospect of needing to do a bunch of sales calls (thankfully that never actually ended up happening).
I keep some plants on my desk, that I am not so good at keeping alive. I also keep some smallish stones to fidget with, when I am thinking, as I am generally a very tactile person. When I really need to focus and tune out the room, I put on my ridiculous pink headphones and listen to some music. Also of note, always keep a glass of water and a mug of coffee at hand; the mug is short and squat and pleasantly round, fits in the hand nicely.