Based on the alphabet designed by Edward Johnston for the London Underground, Eric Gill’s Gill Sans has become one of the most popular Humanist sans serifs around. It’s strokes take influence from real pen strokes, with moderate to high stroke contrast and a diagonal axis.
You can use Gill Sans for most things—it’s Humanist forms make it readable in long-form text, while its character makes it visually interesting at large sizes.
It’s amazing how many tiny differences there are between different fonts and how much of an impact they have visually! It always fascinates me.