Cortland 444 Peach DT. I use it on my 3wt B IIt, 4wt Z X L, 5wt S P / R P L / D S, & 7wt R P L. Most of these rods are medium action rods, especially the B II t & D S rods.
Unfortunately, Cortland's company has gone through some changes and I'm not certain as to the future of this product. I do have Hook & Hackle DT 5 on a back up reel. Seems to be somewhat similar to the peach line in its characteristics, being very supple. Seems to have a different, narrower, diameter and an olive color.
I do have Rio Gold on my 8-weight 9 9 rod. That is the best weight-forward line I've used. I have three or four seasons of use with this line and with proper cleaning care, it is still in great condition.
Rio Steelhead/Salmon line on my Z switch rod. That is fantastic nymphing line on a switch rod.
I think I am happy with the Gold & Steelhead/Salmon lines because they have longer front tapers (50ft on the Gold, 64ft on the Steelhead line) which perform, within most practical drifting distances, much like the DT lines I prefer.