Block guild solicitations in whispers and public chat channels.
Messages that look like guild recruitment spam are blocked from General, Trade, and whispers. There are no notifications to you or the sender, no dependencies on other addons, and no options to fiddle with. It just works (though only for messages in English right now).
It will automatically disable itself while you are unguilded and have disabled the "Decline guild invitations" option in the default UI, since presumably this means you are interested in guild invitations.
Download link and more info:
http://www.wowinterface.com/download...4-NoGuild.html
Motivation:
I actually wrote this several years ago when guild perks became a thing and people started spamming guild invites left and right. Then I started using BadBoy + BadBoy_Guilded and put this project on a shelf for a while. However, I eventually found BadBoy's "arms race" approach too frustrating since I'd have to wait days or weeks for the addon to update to block every unique spam pattern, and when its author announced he would no longer even try to block guild spam in General/Trade chat, I took the opportunity to ditch BadBoy and dust off my old guild spam blocker.
Rather than try to match whole messages, NoGuild just assigns scores to individual words in the message. If the sum of word scores in the message is too high, it's blocked as spam. The word lists are short and simple, but extremely effective. I haven't seen a guild ad in months, except when I've disabled the addon to make sure people are still spamming (yes, yes they are). It keeps a log of blocked messages, and despite checking the log every so often I've never seen a false positive.
If you have specific complaints about the addon's functionality, please post a comment on the download page. Feel free to post in this thread for more general discussion. Also looking for people interested in helping build good filters for non-English guild spam.