Sortd - Rated the #1 App for Gmail
Shift - Shift is the ultimate email client for managing Mail, Calendar, Drive, Slack, Asana, Jira, Evernote, and all your other favourite apps
Drag for Gmail - Transform Gmail into organized To Do lists (like Trello)
Mia for Gmail - A desktop email client for your Mac, without a browser !
Get My Receipts by cloudHQ - Organize your receipts in one click
Mailplane - Mailplane is the best way to use Gmail on your Mac. Use an unlimited number of accounts, get new mail notifications, use plug-ins and much much more.