The main pieces of test equipment I keep around are things like a capacitor tester than can check for shorts and leakage at higher voltages than a handheld, and a signal tracer with an AM demod built in. They're just useful things for basic equipment work, and they still perform their functions. I have a couple of other pieces, but those are collectibles because they're simply not useful anymore. A 1" o-scope still does it's job, but I can buy a handheld with better bandwidth for $50 or less. I do, at times, just build something for the fun of it, the last time I did that was a type 80 and an eye tube along with some bits and pieces of (literally) broken PCB to drive the eye. It was fun, then I tore it down because it was sockets held in clip stands and jumpers and the AC line being directly rectified and thrown on B+. The 6BQ5 is a fun tube, I used to have an amp with four of those as push-pull in the final. You could cook with those they ran them so hot.