Best one I ever heard was the EBS Test Rock 103 used to run back in the late '70s. It was a straight read of the old :30 copy..."This is a test. This is only a test. If it had been an actual emergency, you would have been instructed...etc."
The only thing unusual about it? It was read in a very heavy Russian accent, quite breathy with deep chuckles every now and again. It made your skin crawl in those scary days, but it never failed to crack me up completely. I cannot, for the life of me, remember who recorded it for us, but he was very good. That's another one of those pieces of audio I didn't think to archive, but wish I had.
Rob, do you remember this or was it before you arrived?