TXTableView is a subclass of NSTableView that allows the user to show or hide table columns by any of three methods:
- Control clicking (context clicking) the table header and picking columns from the contextual menu.
- Clicking the top right corner widget. Again this pops up the column contextual menu.
- Through a separate table inspector GUI (probably just a list of check-boxes).
Thanks to the members of the Mac GUI Dev mailing list for suggestions.
Screenshot:

(Update: Removed https scheme from the source URL)
(Update 2: A bzip2 archive of the current snapshot of the source code is available here: http://toxic-public.googlecode.com//archives/TXTableView.tar.bz2)
(Update 3: I failed to specify what license this code is under. Well feel free to do whatever you want with it – it is released under the public domain.)