Galaxian, you can't go wrong with it. I consider it to be my favorite game of all time. I cannot possibly count how many quarters I sacrificed to those machines. How awesome they were.
But, now I can't find them in any arcades ever. Oh well, it came out in 1979, so I guess I can't expect it to be around forever.
If you are confused about what Galaxian is, look at the webpage below this writing.