What are some good everyday monospace fonts?

What are some good fixed width fonts for everyday use rather than just coding and text art? I'm looking for something with serifs, and i'd like to add a couple characters that don't exist in Unicode so something with a license that permits modifications is good. Lowercase numbers i could take or leave.

Apparently typewriters were mostly fixed width (i think, i've never used one) so a font based on a typewriter typeface should be fine but a lot of what i can find is proportional or just ugly.

Thanks in advance.