When you no longer want a particular application or any of its preference files and other ancillary files, AppZapper will delete them all for you. CleanApp does the same, but AppZapper also offers you a convenient place to store all the purchase information for each app (date of purchase, the company's website, the licensee's name, and registration key). It also offers a "Hit List", where you can scan your list of applications and delete the ones you don't want.
(Ars Technica) | Cost: US$12.95 | Requires: Mac OS X 10.4+ (10.6+ for v.2.x) | For further info...