Eurostyle.
That was almost too easy.
If you're in the sign business, there are always going to be fonts that slip your mind or you just can't remember what they are, but there are some fonts, that are so basic, that not knowing them is almost impossible.
As you use fonts, make a list of them and place them somewhere, so you can see your favorite ones or widely used fonts. Write them in the style they are, so that at a glance, you can identify them.