To listen to some conservative JWs, drinking alcohol is banned.
One of the biggest arguments that I ever had with another JW while I was still one was over alcohol. I had just turned 18 (the drinking age back during the last millenium) and was enjoying the legal use of alcohol (I was enjoying it before, but not publicly).
Anyway, my mother and a "concerned" elder tried telling me that it would be best if I didn't drink at all. I kept asking for scriptural principle behind that and they couldn't provide any. They provided plenty of WT publication references...which didn't condemn alcohol, just the overuse. When I tried to point that out, they said that if one does not use it all then the there is no chance for abuse, so like good little followers of Jehovah, we should be babes as to badness and run away from the bad things, alcohol being the bad thing. I argued til I was blue in the face, but to no avail, they couldn't even accept what was plainly written.