Metal Slug 2

Gameplay in Metal Slug 2 is very similar to the previous game; the player (s) must shoot constantly at a continual stream of enemies in order to reach the end of each level. At this point, the player confronts a boss, who is usually considerably larger and tougher than regular enemies. On the way through each level, the player can find numerous weapon upgrades and "Metal Slug" tanks. (wikipedia.org).