Wow. I finally know the name of the cartoon show that only I remember. Star Blazers, apparently. It was this kooky show about these people on a giant submarine-looking ship that had a gun they could only fire once per episode, and it would use up all the power on their ship to do so. Great show, as I recall, but no one else ever saw it, I guess. Anyway, here is a link to some info about it - click here.