For me the one I would like to repeat is the Ptarmigan Traverse in the North Cascades. I made the trip in 1969 and again in 1973. The traverse follows the spine of the Cascades from Cascade Pass south to Glacier Peak and goes through some of the most spectacular alpine country in America. You can do a short version of the trip exiting via Bachelor Creek but you miss some excellent climbing that way. It is mostly off-trail and more than just backpacking because of numerous glacier crossings and tempting mountains but is certainly worth the effort of hauling the climbing gear along. I'd do it again in a minute; not sure my body would though!