I discovered this on accident when I was trying to loot and drag something off the ground and accidentally bashed a chest over Red Prince. Damage wasn't terribly high, but practicing around a bit you can get some decent speed on a good toss. Haven't tried it to try and actually damage enemies though.. Just clicked and drag the item and let go of the button while it's still in range (cursor doesn't turn red but stays white) and it should fling it.
