Overkill
Overkill is a system designed from the ground up to be easy to get into¸ and it's designed to allow for rapid generation of characters and enemies meaning it can be less than half an hour from picking up the book to starting your first game. To help with this instead of using various different dice¸ the game uses playing cards¸ any old deck will do. This allows it to be played in a cabin in the middle of nowhere¸ on a plane¸ or at the classic basement table.