"Like a gold coin on a dunghill"
As a member of Toastmasters (toastmasters.org), I am always on the lookout for metaphors that I can use when giving speeches. As a numismatist, I like when those metaphors include references to coins. So I really enjoyed the metaphor I came across while reading an article in the UK's Daily Mail:
"The brief flash of truth shone out like a gold coin on a dunghill."
Although the article has nothing to do with numismatics, the metaphor is one that I'm sure I'll find a use for in the future. Here's a link to the article if you are interested: Link