Harlan W S
A loop over Sentinel, near Lake Mead, involves some incredibly varied terrain, at the hairy edge of class 3-4 in the descent down the red canyon. Almost everyone I have taken found this peak to be an extraordinary experience. Thank goodness it doesn't appear on anyone's list, and most people lose interest when they discover this summit was not blessed by some august body.
Nick N first told me about this mountain, and sent pictures of his climb in 2002, at a time when I was suffering from brain damage. I remember those pictures well, and kept them as inspiration until I finally got to the peak almost 3 years later. Lee S (of the Vegas Sierra Club) could see the peak from his home in Boulder City, and long ago named it Rainbow. Ed Forkos was the first (I know of!) to put a register on top, and used the name "Sentinel," apparently for consonance with the nearby named "Guardian" Peak. That register disappeared in 2009, between my two visits to the peak a week apart, and I strongly suspected someone was shadowing my website, looking for registers to remove.
My original route followed Nick's track, including a difficult crossing of Razorback Ridge; HTMM later suggested an easier way from near RedStone Picnic area. Link to trip report for Sentinel (Rainbow Lake Mead)