There are a number of top feed weapons. Calico SMG, Bren gun and the Czech one that it traces its lineage from. The Australian Owen and F1 SMGs as were mentioned before and the Stoner 63A Automatic Rifle which is the first picture in this thread. The FN P90 is a top feed too.
and the old gatling guns that were around after the civil war? top fed, mounted on two wheels and hand cranked... remember seeing them in that Teddy Rosevelt movie where they invaded Cuba or was it Mexico?