South Face, Petit Grepon, III, 5.8: The uncontested best rock climbing route on Longs Peak.
Three routes in RMNP are included in Steck-Roper's Fifty Classic Climbs in North America. As mentioned, there are better routes on Hallet's than Northcutt-Carter. There are better routes on the Diamond than D1. This, the Petit South Face, is the uncontested classic Colorado climbing route, and one of the most superb routes I've climbed in my life.
Eight pitches, wonderful climbing, awesome exposure, then finally shimmy along the top of the Petit with legs dangling over nothingness on either side to reach the rappel anchors. There are other great spire routes in the park, on Sharkstooth, the Sabre, Zowie, but this one is the best.
...By John Bicknell, Colorado Mountain School