Joe

Joe is a janitor who works in the main train station in Chicago. He first appears in Small Favor.

Small Favor
In Small Favor, Dresden got to see Joe on a regular basis while travelling and working for the Paranet.

Word of Butcher
He might be a character of interest based on the author's comments in his 2014 Reddit AMA, possibly referring to Uriel appearing as Jake at the end of Small Favor.

"Is Joe the janitor at the train station in Small Favor actually just a janitor, or is he, like Uriel, an angel in disguise?"

"No comment."