https://www.browserleaks.com/
http://www.whoishostingthis.com/tools/user-agent/
http://www.useragentstring.com/
http://gs.statcounter.com/detect
http://www.useragentstring.com/pages/useragentstring.php
http://udger.com/resources/ua-list
http://www.user-agents.org/index.shtml