What's the best and/or favorite piece of equipment you've owned? And do you still own it?

My favorite is my 833A single ended triode stereo monoblocks. I could never afford to buy manufactured ones ($350,000 for WAVAC and a "cheap $60,000 made in Poland.) I built my own with all the design features I want and could not count on getting if I could afford one from a manufacturer: polypropylene power supply filter capacitors in a pi network with the chokes on the negative side for grounding safety instead of inferior electrolytic caps, Hammond 1642SE output transformers good for 4kV carrying only 1kV at which by battery polarity reversal tests on the zero bias grid shows the same current change from the modest 20 ma plate current so I know it s respectably linear and which sounds spectacular, The Hammond transformer is good for 300 ma. This is a marriage made in Heaven for Magnepan speakers which are more than loud enough running the tubes so modestly and allow that SET sound without the need for complicated cones, cabinets, and crossover networks that are sensitive enough for less powerful tubes such as the 300B or the 45. I drive the 833A grids through Lundahl transformers with 45s and these with choke loaded mu follower 2C22s directly with no need for capacitors n the signal path. It took me over two years to perfect this system and I desire no other.