Best Open Source Software

This is a BOSS thread, let's see what turns out to be our favorite open source software. For me, it's definitely GIMP, the gnu image manipulation software. You can get it at http://www.gimp.org/

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>>5
Yeah, I hate it when some asshole finds a bug in my flawless work of Art.  I solved it by setting up a bugtracker with a bot that insults reporters and closes bugs randomly.