Third-party integrations — which ones matter?

We are scoping integrations for later this year. Which tools do you use every day that INFIRISK could talk to? Common asks so far: Xero or QuickBooks for invoicing, Google Calendar for scheduling, Outlook for email sync, Dropbox or OneDrive for document storage, WhatsApp for client comms, Zapier for everything else. Vote with a thumbs up or reply with your own request.