Vanguard, SNK, 1981

Vanguard is an ancestor of later shoot 'em ups such as Gradius and R-Type. Vanguard was the first scrolling shooter, in which you can shoot in four different directions. Also, avoiding obstacles while shooting enemy ships in the air was a new development. As if that wasn't cause for enough stress, the aircraft also runs out of kerosene if you don't fuel up regularly. Vanguard is a horizontal shooter until the last level, in which you have to conquer the field vertically.