I’m an ammunition reloader, got to recycle you know, and I’ve got gauages for each caliber. A reloaded round should drop in and not stick out the bottom. The cases base should fall between the two machined steps on the gauage.
Lyman Reloading 308 Win Case Length/Headspace Gauge https://www.amazon.com/dp/B002RJURSM/ref=cm_sw_r_cp_apa_a3BLzbT1CT546
I have one of those too!
I have found that an endocervical brush makes a pretty good tool for cross-pollinating gesneriads.
I have one also and I use it now more than when I was around airplanes.
Motorcycles
Wire repair as I use a lot of baling wire for seasonal things.
Am I being whooshed?
I doubt anyone has a cooler appliance than one designed to make milkshakes.
Numerous bike cleaning & repair tools, including a snowflake. (In days of olde, one could use something called a “phonebook”.)
Custom designed &/or built camera mounts to get aerial shots.
Does a hearing aid count ?
Looks like those could be also used effectively as a sap or blackjack.
Bicycles require a surprising number of specialty tools. Removing the cranks, removing the cassette from rear wheel, tightening the wheel spokes, etc. It seems each set of bearings (steering, cranks, wheels) requires a different specialty tool to remove and install. Actually several tools each, because there are multiple different standards for each.
But my favorite is the derailleur hanger alignment tool. The “derailleur hanger” is the bit of the frame that sticks down below the rear axle, where the rear derailleur attaches to. If that’s bent out of shape, no amount of derailleur adjustment can make the bike shift smoothly. It’s a simple task with this tool, but almost impossible to do correctly without this tool.
Great for when your woodworking requires precision to the ten-thousandth of an inch, yes? 
You are right though, a pair of 123 blocks is amazingly versatile–one of those tools that doesn’t have a specific purpose, but comes in so handy.
Bone folder for putting a sharp crease in folded paper. It’s actually made of plastic, but they are still called bone folders. The back of a toothbrush or comb works just as well, but this is cooler. 
maybe not cool, but cooler.
I want one of those!
I see them being used on “How It’s Made” for things like custom book binding and high end wallet production. It looks like a plenty useful gadget for its niche.
For someone who isn’t very handy in the kitchen, I have a few very specific tools. How about: [ul]
[li]Radish rosette maker[/li][li]Cherry pitter[/li][li]Plum pitter[/li][/ul]All are made from German cast aluminum with stainless steel where needed. They’re going to outlive me.
DMC Safe-T Cable; replaces traditional safetywire. It’s ok, but I can usually do 3-4 traditional safeties in the time it takes to walk to the toolroom, get the DMC kit, check the calibration date, and drag it back to the aircraft I’m working on. It’s also *very *expensive.
Cable tensiometer; used with a calibrated thermometer to check the tension of flight control cables.
Propeller protractor; used to determine propeller and rotor blade angles, relative to a fixed reference plane somewhere on the aircraft (usually the prop hub or rotor head).
Composite tap hammer; used to “tap test” composite structures to detect delamination and debonding. You haven’t lived until you’ve tap-tested every square inch of a 25ft long, 24in wide S-92 main rotor blade*… upper and lower surfaces… four times.
I could go on, as aviation maintenance is quite literally full of single-purpose specialty tooling, but this is a good representation of things I use often (and in the case of the tap hammer, I actually own one).
- Photo is to illustrate scale; I’m not in it or affiliated with it. Here’s a link to the backstory.
I’ve got an original one! The base is Sea-Foam green.
Well, the press looks like it’s only wide enough to hold down a couple pieces of bacon without them still sticking out on the side. Now, if you had a rectangular press to be used in a square pan, that’d make more sense to me.
That, or, Canadian Bacon is round…
Q-Max cutter, makes holed in thin sheet plate, especially used for making clean holes into terminal boxes or conduit entry points - far better than a holesaw.
Fibreglass abrasive pen, used for contactor maintenance - you basically scour the dendrites that form on electric switchgear - stops them getting too rough and either welding or burning out.
https://www.maplin.co.uk/p/abrasive-fibreglass-pencil-kr61r
Here is something that older dopers might want - get off my lawn you young whippersnappers!
[quote=“casdave, post:57, topic:793369”]
Q-Max cutter, makes holed in thin sheet plate, especially used for making clean holes into terminal boxes or conduit entry points - far better than a holesaw.
[Quote/]
Here in the US I’ve always know them as Greenlee punches. Available in various sizes and shapes.
I have a number of specialized tools for scale modellers:
A hex punch & die set, for punching scale bolt heads from thin plastic sheet. Most recently used to add 168 track pin heads to a set of military vehicle track pads.
A photo-etch bending tool, for precision bending and forming of photo-etched scale model detail parts.
And one I haven’t used yet, a leaf punch set, for making realistic leaves to add to model bases, dioramas, or improvised camouflage.
If you are doing the whole wall, you don’t really need this tool. Just pull the nails and pop each piece down. The tool is for loosening one panel in the middle of the wall.
Dennis