Caliber .50 (1991, Mega Drive)

Caliber .50 is a shoot'em up. It was originally developed by Seta Corporation for the arcades (the arcade version was named Cal .50 in the US and Europe, and Far East in Japan). It was ported to the Mega Drive/Genesis by Dragnet and released by Mentrix Software. It came out in North America only.
You play a jet fighter pilot who crashes down in the jungle and gets arrested by enemy forces somewhere in East Asia. 20 years later, you are able to break free of your prison and obtain a weapon. Now you need to fight your out of this place.
The game uses a top-down view. There is no time limit, no auto scrolling, and you sometimes need to find out which way to go. Your weapon has unlimited ammo, and can turn around 360 degree in both directions while walking. Many enemies leave bullets after being shot. Collecting these will increase a bar. If the bar is full, you get weapon upgrade. If you're shot the damage will first downgrade your weapon and deplete the bar before you loose a life. There is also a limited amount of hand grenades you can throw. There are several items you can pick up. Apart from extras grenades, you can increase the range of your shot, get a temporary invincibility, clear all enemies on the screen or replenish your health, for example.