Most of the rocks around Vegas are sharp! Aside from a few slabs of smooth sandstone found in the Red Rocks Canyon Conservation Area, the rocks that make up most of the mountain bike trails in the region feature sharp edges, ripples like razors, and abrupt ledges... all of which seem perfectly designed to shred your tires to bits!
Combine these sharp rocks with shifting sand and rolling gravel, and you have the perfect combination for ultra-technical, demanding mountain bike trails. Indeed, Vegas is renowned for the technical challenge found on its trails. Bootleg Canyon is the most famous trail system in the area, and it has historically seen full-blown downhill races held on its steep, technical trails in years past. Even outside of race day, you can tackle absurdly difficult lines that blast straight down the southern side of the mountain at Bootleg Canyon.
Bootleg doesn't have a corner on the technical market, however. The Cowboy Trails offer fantastic double black diamond pedal-driven loops. The terrain might not seem that intense on the climb, but when you point your tires downhill, you'll find yourself launching big ledge drops and sliding sideways into exposed corners, blasting through rock gardens, and rolling rock slabs.
Finally, the trails on Southwest Ridge aren't quite as technical, but they do deserve an honorable mention. You can find plenty of ledge-filled tech on these trails, and the accompanying doses of dramatic exposure ratchet the consequence level of this ride to 11! (Well, it's no Hangover Trail, but you definitely won't want to fly off the edge.)
If you're looking for a playground of technical mountain bike trails, but you've already checked off most of the epics like Moab and Sedona, consider Las Vegas as the destination of your next mountain bike road trip.