Tor is one of the most widely used anonymous surfing proxy servers used on the web and as the name suggests, OperaTor is designed for the specific needs of the Opera browser.
OperaTor is a portable software bundle which allows you to browse the web anonymously and actually combines Opera, Tor and Polipo. The developers assure that no privacy data is stored on the computer that you plug your OperaTor pendrive into. You'll experience no difference in browsing other than every HTTP request will be conducted from an anonymous IP - great if you want to hide surfing habits or prevent yourself being tracked.
If you use Opera regularly but want to ensure your privacy then OperaTor is a quick, easy and portable solution.