Swiss Army knife (they're sooo well made)
Under armour underwear: no seams, last ages, extremely comfortable.
Darn tough socks: extremely comfortable, last forever, never smell.
Altra Lone Peak trainers: foot shaped, light, comfortable, quick-dry. Right now every pair of shoes I own are Altra (but I'm trying out Topo Athletic phantom 2 next)
Gore-Tex. And Neoprene.
Docker. People like to hate a winner, and they've gone the paid route, and they did just take already-available kernel features and wrap them up... But man, they did it well and they revolutionised software development and deployment.
Debian, XFCE, Tailscale, Syncthing, rsync, ssh, ffmpeg