Show us the best designed Windows (Phone or Tablet) apps you use

[Note, yes this was stolen from the Apple Core.]

Windows 8 (and by extension Phone 8) have been around for a good chunk of time. Even though not entirely covered from The Verge, I think that there are at the very least, a good number of well designed apps in the store.

Post what you think is the best designed app!

NextGen Reader: http://apps.microsoft.com/windows/en-us/app/nextgen-reader/30648d7a-f0b5-4719-8ca9-7ed6ce3b4b9b

Nextgenreader_medium