Squirrels are the bane of bird feeders. I went though a half-dozen plastic and wooden feeders before I bought an Eliminator from Wild Birds Unlimited. It has a weighted, adjustable perch which allows lightweight birds to feed but slams a door over the feeding portals when a squirrel gives it a try. Reviewers also give high marks to the RollerFeeder ™.
I recently spent several enjoyable minutes in front of a store video player watching squirrels attempt to master a Yankee Flipper ™ bird feeder. A motorized perch spins around when a squirrel grasps it. Although pricey, this feeder is guaranteed to tempt you to produce a video of “Stupid Squirrel Gymnastics”.