Here is my personal collection of gear.
Test and Measurement
Oscilloscope: Tektronix TDS210
Yes, this scope is very old. But it has been sufficient in helping troubleshoot communication protocols, timing glitches, and other waveforms. Bought two of these from my previous employer so I have one for spare parts.
Multi-meter: Fluke 115 (+ mandatory alligator clips)
Had my brother not bought this for me for Christmas, I would probably be using a lower cost multi-meter. What can I say about it? It’s been very reliable and has helped me develop and test countless things from circuit boards, to my furnace and hot-tub.
Logic analyzer: Saleae Logic 16 (original)
This was an expensive tool, but it’s been priceless in its effectiveness. It was very helpful in finding faults and glitches on communication lines. I’ve also found it useful for firmware debugging by using a four bit GPIO output to tell me what functions are being run (when not using a step through debugger with breakpoints and asserts). I really liked that their software could run on a Linux OS too.
Variable power supply: Mastech HY3003D-3
Two adjustable 0-30VDC 3A outputs with switches to channel them in series or parallel without need for external jumpers. Current limiting has been very helpful especially during new circuit bring up, or troubleshooting a broken device in the home. I’ve never characterized the power linearity, stability, or noise but for my purposes up to this point it has been very handy and reliable.