Peak Scanner is pretty fun to have if you live in or are visiting a mountainous area. You point your phone at a mountain and it tells you the name of it, how tall it is, how far away it is, etc..
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Notion, hands down the best note taking app. For project and task management, Asana too is great. They're useful apps to have both on computer and on mobile, but having them on the latter saves me quite some time every day.
Spotify for music is a must.