Font Awesome icons we are still using:

• fa-times + fa-times-circle
• fa-check + fa-check-circle
• fa-clock + fa-clock-o
• fa-user-secret
• fa-bolt
• fa-sort + fa-sort-desc
• fa-sort-alpha + fa-sort-alpha-desc
• fa-print
• fa-remove
• fa-camera
• fa-lock
• fa-spinner
• fa-trash + fa-trash-o
• fa-angle-double-up + fa-angle-double-down
• fa-angle-right
• fa-warning
• fa-eye + fa-eye-slash
• fa-exclamation + fa-exclamation-triangle
• fa-search
• fa-send
• fa-info
• fa-qrcode
• fa-cube
• fa-plus
• fa-comment + fa-commenting

Replaced most of them in #5938. List of remainders:

• fa-sort + fa-sort-desc
• fa-sort-alpha + fa-sort-alpha-desc
• fa-spinner