Recs.
Updated
OsmAnd Maps & Navigation is a free map and navigation application that utilizes OpenStreetMap data.
SpecsUpdate
Pros
Pro Based around crowdsourced OpenStreetMap data
OSM provides a map editable by everyone; just like the web-based encyclopedia, Wikipedia.
Using a community edited map allows one to correct isses they encounter. Combined with the monthly turn around, these edits are added for navigation quickly.
Pro Excellent general map viewing
Sometimes one needs more than just navigation, they have a need to view a map or specify a specific route. OsmAnd provides a very nice, detailed map. This can be good for seeing what is around you or showing a place you are talking about to a friend.
It also provides a means to add waypoints on the map which can be used to dictate a specific route (not simple enough to do routinely).
Pro Has an option to FAVOUR (rather than avoid) unpaved roads (remember when you have this selected!)
This helps in avoiding often congested main roads and in casually discovering alternative routes, sometimes dirt roads as well, which are commonly far less-travelled in most places. Odd place for this option though, should be near the section where you can select which types of roads to avoid instead.
Cons
Con Terrible address data
This is a limitation of OSM's data, but it is unreliable for locating an address while offline. Even with internet it doesn't appear that it can locate most addresses.
Con No recorded voices can be found for download, only text-to-speech
Though not generally a problem, since OsmAnd+ favours TTS-based voice prompts it does advertise also supporting recorded voice prompts. However they cannot be downloaded or selected anywhere in the app, so you'll end up with awkward pronunciation, depending on your device's TTS engine, especially when setting your language to English in a non-English speaking area. Disabling street names will help as a limited workaround, but for those looking for clear and well-pronounced instructions, it's better to look elsewhere.
Con Being based on OpenStreetMap data can be lacking
The use of OSM also has the drawback of many places not getting the attention needed for updates. Depending on the geographic location OSM may have the most detailed maps or the most bare/outdated map.