Most memorable for me were the Virgin Narrows (out & back day hike) and Angels Landing, ten years ago. In the Narrows you walk between soaring rock walls on either side, and your feet are in the shallow (with a deeper pool or two) Virgin River most of the day.
Angels landing is 5 miles roundtrip with 1500' elevation gain, and some people can't handle the last section which is up a narrow spine with thousand foot dropoffs on either side. Posts with chains are provided in the precarious sections. It's not technically difficult, but psychologically daunting. The view from the Landing (at the top) is awesome. The only part I found scary was passing the conga line of people coming up as I was going down.
