Boy they sure make a lot of tools. All kinds of different shape chassis punches and such. I think I'll order one of everything.
I use a Greenlee DM860A, multi-meter and built like a tank. I'll have no hesitation in recommending them... ain't exactly pneumatic though. These are similar to the Brymans range. Dave
I have abused the heck out of Greenlee tools for 3 1/2 decades. Great products. I also second their meters. Rugged & consistent. Ed
Many less expensive unibits have just 1 cutting surface. They will skew from center. For accuracy, a punch or a 2 cut unibit is better. At work, I have to line up as many as 16 holes accurately on a regular basis. We have square & rectangle punches of various sizes, too. Ed
The DB-25 punch is the cat's meow, although few are using DB-25 connectors for RS-232 anymore. If you've ever had to manually file out a DB-25 connector hole, you can appreciate those punches. I had a ton of free surplus/used DB-25 connectors and standardized on them for all of my 12V needs. I just parallel a bunch of pins together for each polarity and leave a gap of unused pins in the middle to prevent shorts, that becomes a 30+ amp connector with gold-plated pins. Most hams would probably just use Anderson Power Poles for 12V, but free connectors worked fine for me.
My big "Greenlee Regret" is selling off my Greenlee Tube Socket punch kit 20 years ago - when I thought "I'll never do tube projects again" It had a punch for 7-pin, 9-pin, octal, Loctal, and a few generics like squares, meter holes etc. The odds of ever finding that complete tube punch kit again are so close to zero as to be zero. Or if I did find it, it would be $1000 on eBay Dave W7UUU
About ten years ago I bought one of the old Lafayette branded hole punch sets. It has been used numerous times since. The new flavor of the month are the titanium coated step drill bits which allow me to use a bench top drill press and drill out successively larger holes. I keep thinking about purchasing a larger 2" and 2.5 inch Greenlee punches for panel meters, but that are pricey!! Roger N6RGR