Google's own mapping, direction-finding and mass-transit locating app, Google Maps, is hard to beat, not just because of its speed and quality but for the sheer amount of information available.
Data includes info about transit schedules (along with service advisories), live traffic reports, bike paths, local searches for businesses and food, turn-by-turn directions (plus alternate routes if you want to avoid back-ups or toll roads) and the ever-useful Street View.
There have been some recent changes in the Google Maps app, some not welcomed by users. For example, Google removed offline maps as part of a general revamp of its apps; there was an immediate and strong online backlash, and the feature was put back.
Available for Android and iOS.