Here are a few of my faves:

• Breezy Weather - Nice weather app.
• Diatronome - Tuner, metronome, and synth
• NewPipe / NeuTube - I haven't found my fave tube app.
• Suntimes - Information and widgets about the sun and moon.

I'm just looking for some recommendations. It's difficult browsing through apps with F-Droid. Thanks!