Since it was one half of the pack-in cartridge for a ton of Nintendo Entertainment Systems, Duck Hunt is probably the game you think of whenever you see a picture of a Zapper.
Duck Hunt, like a lot of light-gun games of the time, is exceedingly simple. There are two things you can do in this game: shoot ducks and shoot clay pigeons. When shooting ducks, your dog will rush into the marsh and flush out the ducks, either one or two at a time depending on the mode. You have three shots to shoot them all in each wave, and must hit a certain number of ducks to continue. Hit them and the dog will pop up with your duck(s) in hand. Miss or take too long and the dog will laugh at your pathetic marksmanship. This frustrated just about everyone I knew that played the game, and they desperately wanted to shoot the dog for laughing at them. While it wasn’t possible in the NES version, Wikipedia claims that it is possible to shoot him in the arcade version, though I was not able to figure out how to do that.
The second mode you could try was shooting clay pigeons. They would fly out from the bottom of the screen two at a time into the distance. You had to shoot them before they hit the ground and, like the ducks, have to shoot a certain number of them to make it to the next round.
I spent hours with this game, simple as it was, mostly because I didn’t have any money for anything new for a few months. This isn’t to say that it’s a bad game, it’s not, really. It’s just at this point, I’m pretty much done with it.