Der Freischütz: a rare chance to see a semi staged performance of this early romantic opera. November 7th Barbican Concert Hall London.
This is a very strong work I'm surprised it's fallen out of the repertory. I've strangely just listened to the old Kubelik version and it was a most convincing performance of the work indeed.
This isn't really unsung - sorry. There are more recordings than I care to list here. Here, for example, is Presto's current listing: https://www.prestomusic.com/classical/works/56381--weber-der-freischutz/browse (https://www.prestomusic.com/classical/works/56381--weber-der-freischutz/browse)
I agree with Alan. It may be relatively unknown now outside Germany (but still popular there) but it's very well represented on disk.