Business Dropbox - worth the cost for the ability to share humongous files and always have everything everywhere. Even if you use something else for online storage, having mobile access is great for keeping a folder of frequently-used manuals, brochures, and such.
Everlance mileage tracker app. Some like MileIQ. Nothing beats efficiency when you can hand over a travel log to your bookkeeper.
Zoom for video conferencing. Screen sharing is your friend. Doesn't get more effective than that.
What are some of your favorite apps of productivity hacks?