Another vote for something that pokes.  It doesn't have to be a broadhead, but broadheads are okay.  A field point with something behind it or a screw or something that will penetrate is important for squirrels.  They are one of my favorites critters to hunt, but they are TOUGH!!!  I wouldn't recommend a blunt of any sort.  They are fine of rabbits, doves, softer critters like that, but not so great for squirrel.  Maybe if you got them right between you and a tree so they took the full force of the hit, but that's rare.  They are awfully quick to jump and make a glancing blow too.  Eons of dodging hawks and owls and other things that fly I guess.