You need create a Chorme incognito.desktop file like with the following contents,
#!/usr/bin/env xdg-open
[Desktop Entry]
Version=1.0
Name=Chorme incognito
Exec=/opt/google/chrome/google-chrome --incognito
Terminal=false
Icon=google-chrome
Type=Application
Categories=Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml_xml;x-scheme-handler/http;x-scheme-handler/https;x-scheme-handler/ftp;
save this file, open a nautilus with root permission. (run gksu nautilus)
Browse to /usr/share/applications and paste the file here.
Now you can drag this icon to your launcher.
Click on launcher icon, chorme will start in incognito mode.