For programming, my favourite is DejaVu Sans Mono. There are many fancy ones out there with hip features like ligatures but I have always found DejaVu the most pleasing to the eye.
For reading, I like Roboto for sans serif. I find it is decently condensed yet easy to read. For serif, I like a paid font called Century Supra. I have pirated this font many times. I also like the serif fonts used by imperialist news outlets a lot as well. IIRC NYT's is straight up called Imperial.
Slab fonts are usually meant for displaying or printing in larger sizes. Like news headines, billboards etc.
Heck, that's probably good to know. Regular serif is cool too lol.