My top app ist Money Wallet, a really powerful financial management package. I use it to administer daily, weekly and monthly income and expenses in different currencies for differenct accounts. Due to it's very powerful and flexible reports, I have a perfect overview of my financial situation in the moment I need it. It is also one of the very few WP apps allowing the import von QIF-files (QIF-import worked flawlessly for me). Withouth that app, I may already have switched to IOS or Android. The functions and power of Monew Wallet are comparable to the legendary Windows Phone Software SPB Finance.
Lockscreen wigitizer is a unique application that will customize any windows phone 8 lock screen using live battery icon and whether forecast. User can choose any photo from gallery and customize it according to need. In addition to that, widget style battery and weather info is available to be display on any point of available lock screen, suitable to your need and requirement.
In no particular order.
Nokia Drive - Best GPS I ever used.
Rhapsody - Listen to what I want when I want
Tune in Radio - Check out all of my favorite radio stations from different cities
Netflix - Need I say more
Office - The Skydrive sync is killer
Ebay/Paypal - 2 apps makes bidding and paying a breeze
Skype - Haven't used it yet but knowing its there gives me peace of mind
You Tube - Works well
HTC weather App - Its cool
Those are the 10 3rd party apps that get the most consistent use out of me. I really wish Pouch was getting more play. Very active dev, has apps for both WP and WP8, but not much love from the community. I use the apps every day; I really hope he doesn't get discouraged and give up.