Scroll lock, break/pause and sys rq keys on keyboards come to mind. They technically still are used for stuff but typically not what they were originally for an

Scroll lock, break/pause and sys rq keys on keyboards come to mind. They technically still are used for stuff but typically not what they were originally for and they could easily be removed or renamed, but still most full sized keyboards have them. Many, many things about computing apply, really, especially in operating systems and programming languages.