OsmAnd - Global mobile map viewing and navigation for online and offline OSM maps
GPSBabel - GPSBabel converts waypoints, tracks, and routes between popular GPS receivers such as Garmin or...
MAPS.ME - Fast, detailed and completely offline maps for mobile devices
RouteConverter - RouteConverter displays, modifies, enriches and converts GPS data between over 75 formats.
HERE WeGo - HERE WeGo - Maps - Routes - Directions - All ways from A to B in one
GPX Editor - Load, modify and save your GPX 1.1 files.