The most useful (and most handled) addition to my fly-rod assortment was a 10-foot Orvis Helios three-weight nymphing rod. If you nymph as much as I do, the extra 6 inches of rod length facilitates precise line and drift control. I was also moving to more high-stick euro-nymphing tactics and a longer rod is even more helpful when you are fishing directly below the rod tip.
I am an avid reader of John Gierach books and he is a cane (bamboo) rod aficionado. I wanted to see what the fuss was about, so when a Hardy 6-weight bamboo road was being auctioned off at a fundraiser for the Kennebago Lake Association; I jumped at the chance to own one.
More recently, my wife and I have been traveling more on fly-fishing adventures. My two-piece fly rods were a pain to take on a plane and checking them risks theft or breakage. 4-piece travel rods are a good solution to this issue and so several have added to my fly-rod menagerie. My most recent fly-rod purchase was a custom build 7-piece travel rod from Maine Fly Company that fits in my briefcase or daypack. It is handsome with its marled wood handle and ceramic guides matching the green rod color. I am going to give it a test drive in late February in the small mountain streams of northwest Georgia. After that, it might accompany me everywhere, just in case!