Most games seem to really give it all they have in the first hour or so of gameplay to get you hooked. What is your most memorable? Mine would have to be Prey. A washed up native american in a shitty town, about to get in a bar fight when "Don't fear the reaper" starts playing on the jukebox when aliens invade, and start using human juice to power its technology. Naturally then you are on your way to saving humanity. Awesome!