Marvel's Daredevil Season 2: 15 Things You Might Have Missed
4. Microchip
Before burning his house down, Frank Castle salvages a disc labelled 'Micro'. Now, the fact that this is the one thing he decides to save makes it obvious that there's some significance to it, but it's what is written on it that's particularly important.
Micro refers to David Lieberman, otherwise known as Microchip. He's the Punisher's sidekick, or the closest he gets to one anyway, who supplies him with weapons and tech. A Punisher series hasn't been confirmed, but if/when it is, expect Micro to make an appearance.
This is also another nod to Agents of S.H.I.E.L.D., as Micro has been mentioned on that show as one of Skye's contacts within the hacktivist group Rising Tide, and given the similarity there we can assume it's the same one.