Taig Lathes : I've wanted a table-top lathe ever since reading about the Unimat in the backpages of Popular Mechanix when I was in high school. Today's answer is the Taig Micro Lathe II (I went for the ER collets and the power feed). Super useful for rebuilding HP cartridge tape drive capstans and making custom tools and fixtures.
Syscomp CTR-201 Curve Tracer : I was thinking about trying to find a 5CT1 plugin for my Tek 5112 or maybe even a full-up 577 but I don't need my test gear to become restoration projects. This unit from Syscomp was less than the cost of a plugin and does the job really well. You can see sample output in the Repair section of my 9100A entry.
Metcal Soldering Station : STB, simply the best. Why bother with anything else? I've got several MX-500P units picked up over the years so I'll never be without one.
Hakko Desoldering Tool : If the Metcal makes it easy to solder things together, the Hakko 808 Desoldering Gun makes it just as easy to take them apart. Like an eraser for solder. There's a newer model but my old 808 does me just fine.