Four 16K ROMs on one 27C512, picked with a DIP switch: building the ZX External ROM board and testing ZX Diagnostics, DiagROM and more on a 48K Spectrum.
After stinking out the building with an open frame laser, I set up the enclosed Creality Falcon2 Pro 40W and use it to cut a hinged plywood box for a 48K Spectrum.
A rusty trunk that sat in my workshop for months turned out to hold a boxed Spectrum+, a Timex Sinclair 2040 printer and a pile of books and tapes.
I once joked that Lemmings belonged in the bin. Its creator Mike Dailly responded with a box of Lemmings, Kester solder, a Vectrex PiTrex and a Bob Ross gummy kit.
A modern recreation of the Mikro-Plus interface that sank Mikro-Gen: built from a PCBWay board, foiled by tall sockets, then fixed and tested on a 48K Spectrum.