Oh I'm pretty sure most people know plenty of knots but don't even think about it. Many knots are useful, but a list off the top of my head in order of how often they come up for me is: overhand knot, clove hitch, butterfly bend, figure eight knot, cleat hitch, slip knot, bowline knot, and trucker's hitch.

I'm certain I skipped many but those are the ones I feel are most common to doing anything useful with a rope. The trucker's hitch and bowline are the ones that can save your life, but the rest are everyday knots that you might already know except for their names. For example, I don't even know what the shoe tying knots are named but everyone knows those.