All control characters are easily typed from the keyboard as well. For instance, a newline can be inputted by typing:

    CTRL-V CTRL-J
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at least, on any Unix terminal I know (and didn't set 'stty lnext' to something else). I can generate characters from the 128+ range by using the ALT key, which is xmodmapped to the appropriate modifier.

I still regulary use passwords with control characters in them - a very old habit I picked up when I first starting using computers. Way back, in the late 70s, we had hardcopy terminals (terminals without a monitor, but a keyboard and a paper roll). Everything a program outputted, appeared on paper. Everything you typed as well, including your password. And paper doesn't have a clear screen function. The only way to not have your password widely known was to use control characters in the password. But you had to be careful, not all control characters were non-printable.... No, this wasn't a very secure system.