Lucky Gun - S1.E10

Nobita has some bad luck so Doraemon gives him a gun which shoots red bullets (actually bursts of light) for good luck and black bullets for bad luck, but no way of deciding which you get. Cowardly Nobita has 3 others try it first and they all get good luck. A little boy takes the gun and shoots Nobita with a black bullet and he gets all bad luck.