Google Voice (until it stopped working well) - I could not have lived overseas for 3yrs w/o Google Voice. An absolute lifesaver while I was making 12-15 transnational trips a year doing both business and grad school at the same time. Google Fi would have been great, but the overall system degraded by then. Concept is amazing and i'd pay big $ for this, I imagine most high end consultants would also.
Apple Music - Seriously, I feel like a thief -- all this music for $10/mo? This should cost $100/mo. I'm on it at least 10-12 hours a day, sometimes even sleep to it. The catalog is extensive. I cross-cut across artists, decades, genres, sub-genres, associated acts, everything.
The Kindle - because I ran out of space for books and never had the book I wanted to read when I was traveling.
Electric Kettle - I make tea 3x as much now because boiling water is so fast and easy.