Cleaner's Issues falsely includes .R3D, .set, sy2, .td3, and .xpi as "Unused File Extensions", but my files include all of them.
*.R3D is used by "3D Inspection Systems",
*.set is also used by "3D Inspection Systems",
*.sy2 is used by "Darn Passwords",
*td3 is used by "TDS-3",
*.xpi is used by "Mozilla" (several of these files are tmp or temp; one is "dictionary_search_latest", another is "xpcom", and the last is "gre".)