Maybe I haven't looked hard enough for these but off the top of my head:

- A universal calendar I can merge across client accounts. As a consultant, I have customers in gsuite, o365, and my personal one and relationship management means manually synching my calendars between them.

- A virtual machine for android phones to sandbox identities and apps into, as I'm not interested in letting a client's MDM near my BYOD mobile.

- A userspace version of Paralells with a linux image that runs on enterprise client's locked down windows thinkpads.

- a Cypher-like graph query language that operates as an abstraction over spreadsheets.

- an excel plugin that de-dups rows and generates Sankey diagrams from selected columns.