Probably Super Mario Bros. 1 at my babysitters' house. I remember the smell of that place.
For 100 lives, bounce on the turtle shell on the stairs in a certain world and you will max out the score multiplier and earn 1up every time you bounce. Or just pick any level that gives you three extra lives, get the lives, and commit suicide. Then you redo it, always gaining lives and dying after you've gotten the lives. They add up fast enough, but the shell bounce is better for efficiency.
Mario 3 is still my personal favorite and I still play it often. Always reminds me of my friends, wherever they are.