Sanford Whiteman is there a list of popular browser values to expand on this? You reference version numbers and such, where can I find the most popular?
Well, for pure browsers this'll give you a glimpse of the permutations: UserAgentString.com - List of User Agent Strings. But it doesn't include the separately identifiable mail clients with HTML renderers (like Outlook).
This file is derived from the BrowserScope UA list: https://raw.githubusercontent.com/tobie/ua-parser/master/regexes.yaml