Mostly adding (my cheat-sheet):

• Brandschutz mit OSM
  • emergency=defibrillator
  • emergency=fire_hydrant - Even if fire-fighting vehicles have a hydrant map for their region on board, an OSM hydrant map can help with operations in other areas.
  • addr:housenumber=num - to find locations fast. particularly important at long streets and large building complex.
• basic needs (and traveling related)
  • amenity=drinking_water drinking_water:refill=yes drinking_water:refill:network=Refill Deutschland
  • amenity=toilets maybe with drinking_water=yes/no
  • amenity=shelter
  • amenity=bench - Great to see where you can have the next rest, when you are on a long distance trail.
  • leisure=picnic_table
  • shop=supermarket or the smaller shop=convenience + opening_hours!
  • tourism=hostel/hotel/motel/camp_site see Tourism
    • Important here: Website, Phone, Mobile, opening_hours
    • Camp Site Office: office=camping (rendered by OsmAnd)
    • tourism=hotel
      • opening_hours:reception=09:00-22:00 osm.wiki/Key:opening_hours:reception
      • check_out=11:00 osm.wiki/Key:check_out
      • breakfast=08:00-11:00 osm.wiki/Key:breakfast
  • shop=outdoor
  • shop=laundry with self_service=yes/no
  • amenity=atm cash is needed in some rare cases
• Hiking/Biking related tags
• osm.wiki/DE:Bicycle/overview_amenities
• sport=climbing
• Sachen für Segler for map.openseamap.org
  • Marina facilities osm.wiki/Seamarks/Small_Craft_Facilities
    • seamark:type=small_craft_facility plus:
    • seamark:small_craft_facility:category=toilets;showers/launderette
  • Harbour-master’s office seamark:type=building and seamark:building:function=harbour_master
  • osm.wiki/Seamarks/Anchorages
• Car navigation
  • Apps like Magic Earth and Mapy.cz show the current speed limit.
    • maxspeed:conditional=30 @ (Mo-Fr 07:00-17:00) - Speed limit in front of school
• Car parking
  • amenity=parking + maxstay=1 hour OsmAnd shows this
• public bookcase amenity=public_bookcase

Loving OSM Services/Apps:

Traveling

• waymarkedtrails.org
• trailimap.com

• Hiking maps of Mapy.cz https://de.mapy.cz/turisticka?x=-4.1274827&y=53.0820073&z=12 (Get the App!)

• Organic Maps: Offline Hike, Bike, Trails and Navigation
• every-door.app - Nice OSM mapping app.
• FireYak to find and map fire hydrants.