Naming a few in no particular order...
Workoutdoors - best fitness and exercise app there is (developer is an active member)
Waterminder - track fluid intake
Stocard - keep store cards on the watch. No more carrying Walgreens, Kroger and the like
Watch Feeds - Get RSS feeds on your watch. Easy to read and also get a notification every time a new article is posted on MR

OTP Auth - 2 FA app. Best there is
wHealth - excellent fitness and health stats app with a plethora of options and complications (developer is an active member here)
Tempo - excellent running and walking stats app with good complications
Heart Analyzer - lots of graphs and daily stats about your heart functions
AutoSleep
Heart Reports - Extensive PDF charting of your heart health that can be share with your provider or just for your own use. (developer is an active member here)
Deliveries app
Strava
News Explorer - excellent news reader. Much better than Apple News