I think Alcohol would be an interesting addition to Day Z. Think about it. It's the apocalypse. Flesh eating creatures are roaming around, trying to tear you to shreds. Maybe you're terrified, and need something to take the edge off, so you take a few swigs of Vodka. Or maybe you broke a leg, and don't have any morphine at hand, but have a few shots of Jack Daniels left to lift a bit of the pain. Perhaps you have a group of Zombies following you, but don't have enough bullets or any traps, but you might have matches and enough alcohol you light a few of them up. Or maybe you're just a bit thirsty. But of course, drinking it comes at a price. Your vision would blur, your shots are less accurate, your character might stumble a bit. Things like that. I think it would be a great addition, and would certainly raise immersion for me.