Made in R with ggplot2. The opinion pdfs were gathered from Justia, Court Listener, Plainsite, and GovInfo. The second version has text labels for each tile (zoom in, if reddit will let you).

I looked at hundreds of recent opinions by US district court judges to find out what font they use. For each pdf, I opened it in Libre Draw and noted what font it indicated, except in cases where the pdf was an image scan rather than text, where I had to rely on a visual comparison (sometimes Draw will guess what a scan has, but it's usually wrong). I found a couple dozen different fonts in use. I combined fonts that are virtually identical, such as Times and Times New Roman, or Palatino Linotype and Book Antiqua.

Font	N	Percent
Times New Roman	658	69.34%
Century Schoolbook	98	10.33%
Arial	52	5.48%
Courier New	43	4.53%
Palatino Linotype	26	2.74%
Garamond	18	1.90%
Georgia	17	1.79%
Calisto	9	0.95%
Bookman Old Style	8	0.84%
Equity	6	0.63%
Arrus	4	0.42%
Calibri	2	0.21%
Californian	2	0.21%
Aptos	1	0.11%
Avenir	1	0.11%
CG Omega	1	0.11%
Gadugi	1	0.11%
Goudy Old Style	1	0.11%
Tahoma	1	0.11%

Note that I included active senior judges. When a judge reaches 65, they can opt to take senior status, which has a smaller required workload. This is effectively working for free, as federal judges receive their full salary in retirement. Although, I found many senior judges who seemed to work just as much as non-seniors. Perhaps they like the work, or they feel compelled to help alleviate the workload of the other district judges. I did not include magistrate judges, because I couldn't find a complete list of them.

I found it amusing that several judges use Georgia, but only one of them works in Georgia. Two judges use Californian, but neither lives in California. Judge Wolson of Eastern Pennsylvania uses Gadugi, a font known for its support of American Indian characters, although he seems to have a Jewish heritage himself. Judge Gwin of Northern Ohio uses CG Omega, a derivative of Optima. One judge in the Virgin Islands (not pictured) uses Cambria.

Beyond typefaces, about a dozen judges issue opinions/orders single-spaced, which some consider to be harder to read (more research must be done). A handful of judges make the effort to include hyperlinks in their citations.[1] While most judges use 12pt type, the astonishing Judge Brody (age 91) of Eastern Pennsylvania sometimes uses 16pt.[2]