Great post! I have used every single one of those apps at one time or another in the course of my productions.
Here are some apps that I frequently find myself using:
1. Flip4Mac: (http://www.telestream.net/flip4mac/) If you need to create a .WMV for a client instead of a .MOV out of Final Cut Pro, QuickTime, or even Premiere Pro on a Mac, you're going to need this tool. It's the only way to control any of the quality settings when exporting to a .WMV on a Mac and is pretty cheap to boot! The free side of this tool will allow you to view .WMV on a Mac so it's a solid download if you buy it or not.
2. Macgo Mac Blu-Ray Player: (http://www.macblurayplayer.com/) If you're like me and you need to burn Blu-Ray discs for clients, this tool is indispensable – especially since Apple has consistently resisted supporting Blu-Ray readers or burners on a Mac. As far as I know, it's the cheapest way to check a Blu-Ray disc on your Mac before you ship it off to a client!
3. iTunes: (http://www.apple.com/itunes/) This is the go-to app for all of my .m4a or .wav to .mp3 or .aiff conversions. Every Mac (and almost every PC) comes with this software so it's virtually available on any computer you're using. The only downside is that you may not want the music you're converting for a client to permanently be in your iTunes library, but it's a small price to pay in order to have a convenient tool!
Hope that helps keep the discussion going!