The problem with knots is that there are so many, and even the most popular ones have serious problems.

For example, everyone recommends bowline, but it's unsafe without securing the working end. Everyone recommends square knot, but it's easy to tie incorrectly (getting a granny knot instead).

Figuring out which knots to learn will take a lot longer than an hour. Here's my list:

Overhand loop, figure eight follow-through, adjustable grip hitch, trucker's hitch, kalmyk loop.