I have an entire garage outfitted with almost anything you can think of and by far the best investment I made, and what I recommend every time this thread comes up on various forums, is a good quality air setup. I’m not talking about a 20 gallon air compressor on wheels. I’m talking about a nice 80 gallon, 3 stage air compressor with a proper configuration. Dedicated hoses to various tools, air drying setup, regulated lines, etc. In my shop I’ve got a dedicated line to my sandblast cabinet, a dedicated line to the retractable hose mounted on the ceiling, and a dedicated line to my shop press. Each lines has it’s own shut off valve, regulator, and water filter. Before the manifold, where each lines breaks off, the entire system runs through a water separator system that it a series of a up and down pipes with valves at the bottom of each down run. The water is denser so it collects at the bottom while the air keeps going through the system. Drain each valve every day and empty the water filters on each line and I’ve got great, dry air. Dry air is the key to a quality air system.
Once you have that, there is an air tool for just about everything and every single time the air tool will run circles around the electric version. Being able to use paint with a hardener, sand blast items, etc. is just a nice added bonus. You’ll never use spray paint again once you’re able to spray 2 part paint.
Outside of that, the stuff I recommend is plenty of outlets, good lighting, a good creeper, a good tool box, and a good set of ratchet wrenches. I find myself using my shop press a lot more than I thought I would when I bought it. I’ve even made several press dies and brakes for it to assist in fabricating other items. Which leads me into another tool I can’t live without but I won’t even get started on or this post will go from a short story into a full blown novel. But it’s a quality welder. I’ll leave it at that.