Ligatures, slashed zeros, clearly distinguishable Il1/O0, not too big of a gap between lines, and maybe script-like italics. My current main monospace font is IosevkaTerm Nerd Font.

I also find the idea of using retro pixel fonts interesting, but so far couldn't get myself to actually try some of the fonts mentioned here: https://news.ycombinator.com/item?id=47708411 .