If you're around my age, you most likely cut your 13 year-old co-op teeth on a little game called Contra. A run-and-gun title that let you play in multiple perspectives, Contra is 27 years old this month. There are no life bars, regenerating heath, or healing kits. If a bullet hits you, you die. It was so challenging that Konami hid a special code in the start screen to give you (and your co-op partner) 30 lives each. Maybe you've heard of it. My friends and I totally beat it without using the code, though.*
*No, we really didn't.