Documentation: Pandoc. I've made books, work document automation, posters, all sorts with this. Pandoc is so useful. Added the mermaid extension to create documents with diagrams, wrote my own imagick wrapper so mermaid diagrams get trimmed to content before being embedded.
PC: Custom built thing with blinky lights, old parts
Email: Airmail got too flaky and subscriptiony. Moved to Outlook.
Editing in terminal: VIM has my love
Architecture diagrams: Visio is key but... windows? bleh. I've tried using DrawTheNet and it's great, especially liking the .git version tracking. DrawTheNet uses YAML to describe the diagram so... readable versions! I converted TOGAF iconography to SVG so now I can build TOGAF diagrams in my local DrawTheNet.