The Pin-Vise The Reamer And The Diagonal-Cutter...

Let us start with breadboard. When possible (almost always) I use Vectorboard with pre-drilled holes on 0.1-in. centers. My favorite being the copper/tin 12 x 12 pad-per-hole. If the circuits are simple I'll use the, again, pre-drilled holes on 0.1-in. centers with solid copper foil on top. It's a lot cheaper and the foil is easy to carve with an X-Acto knife to isolate nodes and provide a big solder-pad for them.

Here's where the first tool comes in. The Pin-Vise. That is the proper name for the tool used to cut threads in holes (tap) for screws. Only in this case, instead of a tapping bit I use a drill bit. I actually keep two always loaded. One for clearing #4 and one for clearing #6 screws.

On most breadboards there is some kind of small screw. Not many. Maybe just even one to mount a heatsync to a regulator IC. Which you want to lay flat (low profile). The Pin-Vise and the pre-drilled breadboard make a 10-second job of this expanding the pre-drilled hole without the need to leave the bench (get up off the chair) for something so trivial.

This can also be useful to prepare a hole to accept the next tool. The Reamer. A tapered, fluted, 'hand' tool use for enlarging a hole, linearly, to a new size. You can go from 1/4-in. to 3/4-in. with this toll. Very fast. Especially in breadboard.

Leading to the last tool that you should already have. The Diagonal Cutter (small). Not only will you need this to trim the component leads but it can also be useful to score the breadboard, with pre-drilled holes on 0.1-in. centers. A little nip between holes (on both sides) and you can snap the board like glass (or tile or sheet-rock).

This also justifies buying the breadboard in larger sheets. When you can trim (shape) it to exactly what you need you get the best use from your material.

Remember... Most breadboards should be considered 'Proof Of Concept'. To You. So... In many cases. The breadboard has to be the chassis also. Many times my breadboards had four posts (standoffs each corner) to elevate the breadboard on the bench above the banana-jacks (power) and connectors (input/output) and potentiometers (control) mounted to it so I could test the function of something I may scrap in the next minute.

Almost every breadboard I made used only these simple tools, along with wire and solder, to demonstrate some very impressive circuits.

Working With Thin Metal - Hopefully Aluminum...

There comes a time when some prototypes need a proper chassis though. Maybe for a design review or maybe a trade show demonstration and even to showing off at the class science fair. For this purpose. I use two additional tools. An electric drill (of course) and a Nibbler. The Nibbler is a tool designed to remove a small amount of metal from any hole it can fit in. It punches out a rectangular (very small) section of thin gauge metal expanding any hole it fits in. When carving out a large rectangular hole you can drill a bunch of perimeter holes and clean up with the Nibbler to the final size saving a lot of time and effort. You can also use the Reamer to enlarge holes that may already be there or holes you drilled that are too small (cause that's your only drill bit).

Outside of the tools mentioned above I can't remember any other tool I used to provide many working, manufacturable, prototypes.

Decorating A Chassis...

Most chassis have connectors, indicators, controls, etc. Quite often it is common to label these. Being a prototype it is ridiculous to consider etching or silk-screening and ugly to use a magic-marker. What I use are 'Dry-Transfer' A.K.A. 'Rub-Off' labels. These are available in many styles and combinations of letters, numbers, words and designs (patterns). Very easy to apply and look surprisingly professional. Usually, after applying the labeling, a fine coat of clear lacquer finish is sprayed, gently, over the lettering to improve durability. You can also use a gentle swipe of clear nail-polish (yeah nail-polish) to protect the label.

You can truly make any chassis look like a production model with nothing but spray paint and Dry-Transfer lettering. Don't believe me. Most, certainly all, vintage scenes of the space program rocket-capsule and flight control room equipment are mostly prototypes. None of that existed before that moment. None of it would ever be used again (replaced). Almost all of it was made, by hand, with this simple method.