Gradius
I have seen Gradius evolve ever since I was a kid. It was a side scrolling spaceship game. You pick up "power up" capsules and get crazy weapons. But the environment get's almost completely full of things trying to kill you. This game takes motor skills. This clip my friend Pete sent me is just ridiculous. Every Gradius game has levels like this. And I never got as far as this clip. FYI for fans of 90's video games.