I've been a fan of CoPilot for many years. The GPS-based satnav app has been around on Android and iPhone for a long time, and has recently made its Windows Phone debut. The basic features are free on Windows Phone, though you will have to stump up if you want to make full use of features like 3D maps, unlimited voice-based turn by turn instructions, speed limit warnings and more. For Android and iPhone you need to pay up front as there's no free element.
And if you do pay up, then the full gamut of features is really impressive. How about dragging a planned route line on-screen to rework it so that it takes you to a nearby place, or the superb ClearTurn 3D visualisation of a road that shows on-screen what you can expect to see on the ground complete with signs and lane indicators.
Cyclists can benefit from routing that avoids busier roads, car drivers can have fuel costs calculated, there's real-time traffic data and you can save the location of your vehicle and then use the app to get you back to it later. That's very handy for when you have to park in unfamiliar places.
OS: Android, iOS, Windows Phone
Price: Free on Windows Phone, Android and iOS prices region dependent