/Applications/Safari.app/Contents/Resources/compass.icns
/Applications/Firefox.app/Contents/Resources/firefox.icns
/Applications/FirefoxNightly.app/Contents/Resources/firefox.icns
/Applications/Google Chrome.app/Contents/Resources/app.icns
/Applications/Google\ Chrome\ Canary.app/Contents/Resources/app.icns
/Applications/Opera.app/Contents/Resources/Opera.icns
Run something like this on your terminal:
sips -s format psd compass.icns --out compass.psd -z resampleHeightWidth 1000 1000
sips -s format png compass.icns --out compass.png -z resampleHeightWidth 1000 1000