We recommend a slightly overweighted floating line. By this we mean if you are using a 6 weight rod, the line should be more like a 6.5 or larger. This will help turn over big flies, cast well into the wind, and load your rod easily at close quarters.
Three of our favorites are:
They all excel at the heavy fly game and still are smooth enough to land a dry fly when you need to. They are also very high quality and will last for years.