Excel
From APIDesign
Excel is almost a synonymum for any spreadsheet program. An example where a product name became de-facto name for the whole technology. I have never learned how to use Excel (or rather OpenOffice Calc) effectively, but I know that non-programmers can do quite amazing things with it.
Cluelessness is always a goal for any technology vendor. Everyone wants to provide a good technology which is easy to use and easy to get productive with. Everyone seeks such holy grail. Excel got quite close. It managed to allow non-programmers to be productive with computers without learning what are the if or while or for statements.
Rich Unger mentioned Excel few times during our DSL presentation at JavaOne2010. Rich said that his company had to design Apex in order to attract people that are familiar with Excel, but are intimidated with Java. Actually when we (and also our audience) tried to summarize when to use DSLs (Rich's side of the shootout) and when to writelibraries (mine point), we agree that it basically depends on whether you are targeting (Java) programmers or not. For people with Excel knowledge the Apex was said to be a better fit.
Our talk was supposed to be a shootout and I used strong trash talk while preparing with Rich, but during the talk we treated each other with mutual respect. I somehow started to believe that Rich's excel argument is true. Apex was the language for Excel audience and it deserved its right to be a DSL, not a library (as the TheAPIBook would advocate).