Developer website: David Nelson
NovoIcons is the best icon extractor. It's simple and intuitive, but has more features than the competition. It can extract icons and export them into PNG, TIFF, GIF, JPG, or ICNS. 512×512 icons are natively supported.
While this version is over three years old, it still functions well. Version 2.0 is under way, but it is barely into development so it will be a long time until release.
- links updated to reflect url change
Mac OS X 10.5 or later