Depends what you're working on... (Score 4, Insightful)

There are a number of pieces of equipment which should be in any lab setup - e.g. oscilloscope, voltmeter/ammeter, decent bench power supply, soldering iron and proper illumination. What you need after that will depend much more on the kind of electronics that you want to work on - digital, analogue, RF etc. Each needs a different set of equipment. Personally, I work in the digital domain, and find a fast logic analyser invaluable for diagnosing difficult problems. I would also include a dedicated bench computer (or two), and large, deep benches with overhead shelves. You can't have too much space. Of course the most important piece of equipment is your brain - no piece of equipment is going to replace your ability to think through a problem.