Hakaiman is an action/stealth game by prolific Japanese developer Ikiki.
Hakaiman "is a top-down espionage game. There are six missions in total, that have you stealing the plans, infiltrating the base, etc., with nothing but a machine gun, a handful of grenades, and your gigantic brass balls at your disposal.
Whether you want to go in guns blazing or silently snap necks is up to you, but guards are thankfully quite simple-minded and, unless they see you, will not actively seek you out (and even then, for only a short while). They will also respond to loud noises, like explosions. It’s not very realistic, but it makes the game infinitely more fun and playable." (Derek's TIGSource review)