This is a video about a fence post-puller I made from scrap metal. It has no moving parts. You mount it on pallet forks. I sized this puller to fit up to a 6" wooden post.
If you need to remove a single post, and when you don't have a tractor, you can also use a car jack. Drill a hole through the post, stick a piece of metal through it, and lift it up with the car jack. Drill the hole high enough so that the car jack fits under it. You might need to repeat the process a couple of times, or use some spacers, and use some wood as a platform for the car jack, but it will get the job done. And if the soil is soft without rocks you can use an earth drill to drill a hole in the soil right against the post that you want to remove, and that will help to make the removal of the post much easier. And sometimes that makes it even possible to remove the post by hand. I used the second option a couple of days ago, and that was the easiest way to do it for me. I used a hand operated earth drill with two blades instead of an auger that is shaped like a screw. Those are cheap, and easy to handle because they are not heavy.