This mashup has been around for a couple years, but, for obvious reasons, it's making the rounds today.
San Francisco DJ Party Ben took the iconic, whistled theme song from The Andy Griffith Show and overlaid it with the vocals from Beyoncé's mega-hit "Single Ladies." They go together surprisingly well. Enjoy. (Via HyperVocal.)*
* This post originally attributed the mashup to the person who uploaded it to Vimeo, rather than the San Francisco DJ who created it.