Google Fonts is awesome it has a lot of beautiful fonts which are free and open source. Here are some of my favourites

Sans-serif fonts

1. Roboto
2. Poppins
3. Open Sans
4. Plex
5. Ubuntu
6. Inter

Serif fonts

1. Roboto Slab
2. Merriwether
3. Playfair Display

Handwriting fonts

1. Dancing Script
2. Pacifico
3. Sacramento

Monospace fonts

1. Roboto Mono
2. Ubuntu Mono
3. Source Code Pro

What are your favourite fonts leave them down in the discussion.