I almost always utilize most of these knots during one weekend of sailing in securing fenders, as stoppers for sheets, or stringing pirates up by their feet. Perhaps I haven't had much need for the last one, but you have to stay proficient for any of those situations.
If you can't tie any of these don't worry. "If you can't tie a knot, tie a lot". I'll be sure to laugh and point the next time I walk by your boat.
Click the picture below to see the knot videos.