One of the first programs Swampy wrote was a tape device driver for
the PDP/8e. He has also written programs for
a Pr1me 650 (this machine was a Honeywell mainframe clone), a Cyber 600 series which was a 60 bit machine designed by Seymour Cray, and the first machine he knew really well, a Data General Eclipse C/330. If you read the book "The Soul of a New Machine" you can read about the design of the Eclipse.
In terms of favorite, Swampy always likes a well implemented system.