There are drugs that, when mixed with alcohol, cause major problems. Most people will tell you not to drink when taking benzos. This is correct, of course. However, there are a lot of people who really believe that 5 mg of valium and a shot of brandy can kill you. It ain't going to happen. One drug that I found that interacts with alcohol is zanaflex. I would go to sleep, get up, experience a "white out".. literally everything looked white. Then, I would pass out. I was lucky that I didn't kill myself before I figured out what was going on.
The other two drugs that come to mind immediately are APAP (you won't kill yourself right away, but eventually your liver will go) and darvon (you'll kill yourself right away).
D