It depends really on what I want to do.
When I want to burn a normal data or audio CD I use Nero 6 simply because it works well. For some audio CDs I also use PlexTools, also for ripping audio CDs.
When I want to do a simple 1:1 back-up of an existing CD I use CloneCD. It works so easy. I don’t back-up many copy protected games but you can also use it for that.
When burning a DVD I use CloneDVD. It does everything for me except decrypting DVDs but DVD Decrypter comes in handy here. You can also use AnyDVD though but I have always used DVD Decrypter and never had a problem.
When burning an audio CD from a CUE-sheet I use Burrrn. It’s freeware software and works great with CUE-files. Better than Nero in my opinion.
Last but not least, when I want to back-up an Xbox game I use RecordNow! because Xbox games I copy with Nero don’t work in an Xbox with a Samsung DVD-ROM. Don’t know why but RecordNow! back-ups always work.
For every task I have my favorite app