Please use this thread to post your font favorites and why you like them.
I use Bell Centennial (remember phone books? this is the font) for specs and dimensions. It was designed to be legible at very small sizes so you can still read 10pt text at 50% print out.
I use Highway Gothic for drawing titles. It comes in 5 widths Condensed, Narrow, normal, Expanded, and Wide. It was designed to be used on road signs, the different widths make it very flexible for titling.
I am now using WildWords, a comic book font with upper and lower case, for notes. I got tired of Graphite, and this font is authoritative without being formal. If I need a font with very tall and narrow letters I use SamaritanTall.
For Code Data, and when I want to be rude in the drawing I use Courier, which, to my eye, is second in deadliness only to Comic Sans.