No ones mentioned one of my faves... Glenmorangie. It is usually pretty cost effective. Has a solid citrus/oak character. I am not sure I would want to use scotch in a beer. It is my understanding that liquors are used in beers to get more of the extracted flavors from the wood itself. So you should really have certain flavors you are trying to extract and then determine if that liquor is going to best give you those flavors or if another medium should be used