Amiga hardware and software
Source: Raymond Chen
On the Amiga (NB), press and hold the following keys:
LeftShift, LeftAlt, RightShift, RightAlt
Now press one of the 10 function keys. (Keep those four keys down!)
Each function key produces a different message.
To get the rude message, insert a disk into the internal drive.
(Still holding down all those keys?) Now eject it.
"We built the Amiga..."
and when you pushed the floppy back in:
"...and Commodore f**ked it up!"
The rude message has been deleted from newer versions of KickStart.
Get 1.2/33.166 or earlier.
Commodore 128
Source: Norman St. John Polevaulter
And of course, going WAY back, there is the credits and anti-war message
You could coax out of a Commodore 128 by typing:
SYS 32800,123,45,6
in BASIC