There are probably as many opinions on this topic as there are Android power users. Here's mine:

Advanced Task Killer: meh!
Better: Elixir; SystemPanel App

Taskos: meh!
Better: Astrid; Best: Astrid (free) plus Astrid Power pack (paid).

DroidAnalytics: meh! mAnalytics: yuck/ugly/limited.
Better: Analytix

Google Docs: unnecessary if you have Documents to Go

Astro File Manager: meh!
Pales in comparison to: File Expert

Shazam: fair
Pales in comparison to Soundhound

Google Finance: meh!
Better: PageOnce and/or anMoney