PVC pipe wrecking ball to knock over block towers/castles. Great eye/hand coordination required to aim, could also vary the weight and type of objects used as the "wrecking ball." Plus, it's just fun to knock stuff down, isn't it?
Might be easier to beef some of these up for kindergarten then try to make other activities appropriate. STEM for Preschoolers 10 Science Technology Engineering Math Ideas for 3 to 4 Year Olds Left Brain Craft Brain Pin