Warlock was the game that, in 1980 at Games Day in London, I wanted more than anything else in the world. My dad overruled me and said: "Let's get this instead - it looks like it will be better". What we got was the Basic Dungeons and Dragons set and he was absolutely right.
Fortunately, with the advent of eBay, I was able to get Warlock too (many, many years later). Next: Valley of the Four Winds.