AdAware is a privacy tool, that scans your memory, registry, hard, removable and optical drives for known data-mining, aggressive advertising, and tracking components. It then lists the results and offers to remove or quarantine the components. The program detects a wide range of adware/spyware related issues and can be updated with the latest signatures via the built-in update utility. The free version is strictly a scanner, and does not provide any real-time protection.

Pros: Good reputation; detailed reasons for detected items,
Cons: No real-time scanning, no automatic updates