Univers 57 has been used by Apple,
Univers 55 is used by Matias,
Filco use
Futura,
Dell used
Frutiger bold on some boards,
Cherry and IBM have both used something like
Helvetica (although purists would argue it's not the same)..
Some very old boards (Commodore VIC-20 and PET are the first that come to mind) used
Microgramma or
Eurostile which is my personal favourite (and there may be something related to this font and keycaps happening soon, but I shouldn't say more until things have progressed a little further...)