I have tried AppZapper, and it's OK. However, when compared with AppCleaner 1.2.2, the difference is STRIKING. AppCleaner does most of the things that all of the reviewers below ask for, it finds ALL of the files associated with the main app you are deleting - EVEN FILES THAT ALL OTHER SUCH APPS OFTEN MISS - it is totally unobtrusive and doesn't impact your CPU or memory AT ALL as far as I can tell, IT WORKS AUTOMATICALLY when you maybe forget to startup AppCleaner and just toss an app into the trash ITS SmartDelete CATCHES IT AND ALSO AUTOMATICALLY CATCHES ALL ITS ASSOCIATED FILES AND OFFERS TO TRASH THEM FOR YOU! And perhaps most amazing is that it is so superior to all other such apps but is FREE, FREE, FREE, FREE, FREE! If you don't believe me, just check out the comments and reviews on AppCleaner's MacUpdate.com (http://www.macupdate.com/info.php/id/25276) and VersionTracker.com pages (http://www.versiontracker.com/dyn/moreinfo/macosx/32740&mode=feedback). That level of user satisfaction is far, far higher than all other such apps, illustrating that people love it for all its capabilities and performance - not just its price (which, again, is FREE!).
When you try AppCleaner, set the preferences to "Protect launched apps," "Protect default apps," and "Enable 3D transitions," don't forget to turn on SmartDelete, then one-by-one select the "Applications," "Widgets" and "Others" icons at the top of AppCleaner's main window, and with each one select the "Options" menu (in the Menubar) then "Select All" to instruct AppCleaner to protect all those apps, widgets and other resources from being accidentally deleted, then you can uncheck one-by-one all the ones that you don't want AppCleaner to protect. Trust me, you'll love this app with it set this way! Enjoy!
(Oh, and BTW, I am in no way affiliated with the makers of AppCleaner - I don't even know them. I just LOVE IT when truly great software is made available for FREE, and I feel such magnanimous developers should be promoted whenever possible, even when it's a bit annoying (as this comment is because it's in another app's MacUpdate space).