If a stone is covering the opening of a barrel, making the contents inaccessible, one may tilt the barrel so that the stone falls off. If the stone is between barrels, so that tilting it will cause it to fall and cause damage, one may pick up the barrel and move it, tilting the stone off in another location. If coins are resting on a cushion that one needs, he may shake the cushion so that the coins fall off. If something repulsive was on the cushion, one may wipe it off with a rag (though one may not use water on a cushion of fabric). If the cushion was made of leather, one may even remove the offending substance using water.
Beis Shammai say that one may remove bones and shells from the dining table by hand; Beis Hillel say that they must be shaken off. One may remove crumbs of bread that are smaller than an olive, pea pods and lentil pods because these are fit for use as animal fodder. If a sponge has a leather handle, one may use it on Shabbos; if it has no handle, one may not use it on Shabbos because it will be wrung out when he squeezes it. The Sages say that either kind of sponge may be used on Shabbos, plus they are not susceptible to ritual uncleanliness.