Wall Street Journal Law blog has a post on typefaces for appellate briefs that's worth your attention. Times New Roman, which was the most popular default typeface for many years until recently, was designed for the London Times to facilitate fast, once-over-lightly reading. It's better to use a font designed for book reading in a brief. They are designed for slower, careful, deep reading. (Just in case someone would think it would be cute to use Courier, a font designed for pre-computer-printer-age typewriters, be warned-- it's judge abuse.) Like SCOTUS itself and the Solicitor General, we're Century people at my place.
Hat tip to Sam Glover (Man, I could a good cup of coffee now.) and Lawyerist.