DIY Map GPS (US$4.99, universal) is a GPS navigation solution for those who like to create or annotate their own maps. While it can use the open source Open Street Maps to download mapping data with an Internet connection, it also lets you create your own maps from JPEG or PNG files. DIY Map also lets you use atlases created by Mobile Atlas Creator that run on Macs and PCs. You can also use maps you have scanned in.
Using downloaded maps means no data charges, so if you are on metered plans that is an advantage.
I tested the app with Open Street Maps data, which does require a data connection. It worked OK, but I did not find the data as complete as Google or the Apple Maps solution. I did like the local weather, sunrise / sunset times and moon phase information that was built into the app.
You can download POI information for your current location, but I found it lacking compared to what Apple or Google supplies. For example, I looked at the POI data while I was sitting in a restaurant, and it showed the closest place to eat as nine miles away.