Essential software tools: i3wm (a tiling window manager for Linux). So much nicer to use than draggy droppy window managers, and so lightweight.
Impactful books: The Fabric of the Cosmos (Brian Greene). Reading this changed my view on the world, mainly due to it helping me get an intuitive grasp of general relativity.
Physical tools: My laptop. I have had a bunch of different Thinkpads over quite a number of years. My work and hobby lives largely revolve around computers so a laptop I like and am familiar with is very important.
Art pieces: Framing and hanging my own photos has been a lot of fun. Next I want to make the frames myself rather than buying them in.
Any other items that have significantly influenced your life or work: My dSLR (Canon 5d mkI & 50mm f1.4), my musical instruments. Also a handful of humans!