I use CCI Standard Velocity more than anything else. Wolf match ammo used to be my favorite but it is nearly impossible to find anymore. SK has also proven to be excellent ammo and seems identical to Wolf. Standard velocity ammunition has always proven more accurate than any HV ammo for me.
Squirrel hunting with a 22 is one of my favorite ways to spend a day when the leaves are off of the trees. You do not need either HP or high velocity for squirrels.