Selectrics get all the hype, but I love the typefaces available on Smith-Corona typewriters from the 1960s. From the samples posted by munk, I think my favorites are the futuristic but legible "Classic Elite No. 86" and the handwriting-style Artistic Script (pictured).
There are about 20 in the set. The only ones that seem to be available as fonts are Numode No. 61, and this set with Smith-Corona's Prestige, Mini gothic and the script, bu all in very roughly-scanned form.
(Via this conversation between @hacklib and Marcin Wichary, who is writing a book about the typewriter and mechanical keyboard community.)