Ask HN: Best software in the world?

This question was originally asked at Barrapunto, a Slashdot clone in Spanish: http://preguntas.barrapunto.com/article.pl?sid=10/10/27/1045237

I'm interested to see what HNers think, so I'm translating it:

"From your point of view, which is the best software in the world? I mean software for end users, MQSeries or a virtual machine with a JIT compiler would not be valid answers. Some examples that come to mind: LaTeX, Bloomberg (real time financial data), Emacs."

In the following discussion, VLC and 'Hello, world!' were the most voted while Excel and browsers such as Firefox or Chromiun were the most mentioned.