Does anyone know if there are many Zion peaks/HPs/viewpoints that can be safely enough climbed solo, class 3 or less, at least besides North Guardian Angel (class 4) and the like?
Here are some (but not all; there are more):
Class 1Deertrap Mountain
Cable Mountain
Class 2Cougar Mountain (not sure about the summit block)
Crater Hill
Death Point
Pocket Mesa
Canaan Mountain (just outside park)
Class 3West Northgate Peak
East Northgate Peak
Checkerboard Mesa
South Ariel Peak
Obscure trails would be great, too
Most trails in the Park (at least the man-made ones) are well known, so they wouldn't be obscure, but here's a breakdown of some (not all) of the trails.
Very Popular
Gateway to the Narrows Trail (2 miles round trip)
Middle Fork Taylor Creek (7 miles round trip)
La Verkin Creek Trail (22 miles round trip plus side trips)
Timber Creek Overlook (1 mile)
Hop Valley Trail (13.4 miles round trip, but connects with the La Verkin Creek Trail)
West Rim Trail (14 miles each way)
Angels Landing (5 miles round trip)
Emerald Pools (3 miles)
Observation Point from Zion Canyon (6.5 miles round trip)
East Rim Trail (18 miles each way)
Hidden Canyon (3 miles round trip on good trail, much farther with scrambling)
Watchman Trail (2 miles round trip)
Pa’rus Trail (3.5 miles round trip)
Canyon Overlook (1 mile)
Popular
Chinle Trail (16 miles round trip)
South Fork Taylor Creek (3.2 miles round trip)
North Fork Taylor Creek (6 miles round trip)
Observation Point from East Mesa (7 miles round trip)
Deertrap Mountain (16.4 miles round trip)
Cable Mountain (15.8 miles round trip)
Sand Bench Trail (3.5 miles round trip)
Wildcat Canyon Trail (6 miles each way)
Northgate Peaks Trail (4 miles round trip)
Obscure
Death Point Trail (4 miles round trip-not sure about current access).
There are many off trail routes that are obscure, but other than Death point, I can't think of any actual trails that would be considered to be obscure. Of course there are a lot of easy off trail routes that would be obscure, but the official trails in Zion are pretty well known.
Easy off Trail Hikes (easy class 2)
Huber Wash (1/2 to full day)
Coalpits Wash (2-4 days depending on route/extentions)
Scoggins Draw (1-3 days depending on route/extensions)
Camp Creek (not sure about current access) (1-2 days)
Lower Beartrap Canyon (2-3 days)
Elephant Arch (1 day)
Timber Creek Forks (1 day)
Barrier Falls from the bottom (2 days)
Subway from the bottom (1 full day)
Lower Echo canyon from the bottom (1/2 day)
More Challenging Off trail Hikes (Scrambling class 2-3 or swimming)
See also the class 1-3 summit list above. In addition:
Zion Narrows (1-2 days)
Deep Creek (3 days)
Parunuweap Canyon (3 days)
Mineral Gulch (2-3 days if continuing into Parunuweap)
Semi-technical Hikes (or or two short rappels/handlines-experience with basic rope skills required for at least some of the party):
Subway from the Top (1 full day)
Orderville Canyon from the top (1 full day)
Lower Kolob Creek (3 days)
Bridge Mountain Arch (1-2 days)
“Easy technical” Hikes (rappelling/rope work plus scrambling-experience required for all members)
Pine Creek (1/2 day)
Mystery canyon (1 full day)
Middle Echo Canyon (1/2 day)
Keyhole Canyon (1/4 day)
Once you get to moderate technical canyons and class 4 summits or more the list gets much, much longer, but I wouldn't solo those.