For desktop the main choice has long been JOSM (https://josm.openstreetmap.de/). Potlatch, the former online Flash-based editor, has now been repackaged as a desktop app (https://github.com/systemed/potlatch3 and https://systemed.net/potlatch/ - disclaimer: I'm the maintainer).
There's also iD (the JavaScript editor embedded in osm.org), of course, and a number of mobile editors such as Vespucci (Android) and Go Map!! (iOS).