Climbers like to get way into the weeds on knots (“but if this one is loaded with a wet dyneema sling around a deciduous tree…”), so I thought this article was admirably restrained, and does a good job explaining why you’d use each. I’d personally say that a figure eight and overhand are necessary, followed by the clove hitch and prusik. The double fisherman is mostly useful for soloing what you just abseiled after your rope gets stuck. ;-)