Well, Fastjack is, obviously.

Netcat is mentioned various times, including the rules for multiple nodes and for the intro to the rules chapter--she's trying to get through a door.
Elijah is mentioned a page later, under buying hits.
Pistons is up next, as the example for glitches.
Then it's Jimmy No's turn, with the Rule of Six example.
Lyran is trying to bluff her way past some go-gangers in the opposed test example.
Clockwork is trying to fix a shot-up prototype under Quick Extended Tests.
Ma'Fan is mentioned under Using Jumping in the skills section.
...
Oh, and Locke, from the Buzzkill story at the beginning of the book, is mentioned under Legwork in the Contacts section.
Those are just the ones that I remembered seeing and had to do a little looking to nail them down.