Favorite PC Software

What is your favorite PC Software?

Examples:
Photo Editing Software
Video Editing Software
Music Making Software
Mathematics Software
Computer Programming Software.
Etc.

Photo editing of course, MP3 editors (to make sound effects a la nooooooooooooooo.com button) converters, downloaders, Google Chrome. And Steam.

I still have to find a good movie editor and an easy to use flash maker for shorts. Anybody knows a good and easy one?

Minecraft.

Photo Editing Software, like GIMP or Photoshop. Those are very good and pretty useful for anything like graphics or any small tweaks to pics. I use them more than other software usually.