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: