Ok, let's get the ball rolling, in no particular order:
ROCKY GAP/POTATO RIDGE - You can't call yourself a serious wheeler in southern Nevada unless you've done this run. There's some nice scenery, the run can be challenging from a technical standpoint, there's a cool sign on the Red Rock side warning you that the road is unmaintained, there's often burnt out or stripped out vehicles on the side or middle of the trail reminding you that sometimes discretion is not the better part of valor, it's close to Vegas and it gets you into the Red Rock NCA for free. What's not to like?
WHEELER PASS - Aside from a crazy lady in a storage container, this is a great route. You spend some time crawling over rocks, there's some great views and it gets you out of the heat. Fun place to play in the snow as well.
BURRO WASH - What's better on a hot spring/summer/fall day than to wheel down a canyon to the Colorado River and get wet? The trail is difficult enough to keep things interesting, and remote enough that you really feel like you're getting away from it all. I think we should all thank Thomas Edison. Without this electricity thing, we wouldn't have a lot of the fun roads we have, including this one.
BIGHORN COVE - This one technically isn't in Nevada, but it's closer to my house than most of the state, so I am throwing it out there. This runs from US 93 in northern AZ down to the Colorado River just south of Willow Beach. (You can also reach the trail through Jumbo Wash from Willow Beach.) You can think of this as the continuation of Burro Wash, as it's the same powerlines for both roads. Compared to Burro Wash, the Bighorn Cove Road is steeper, more technical, has cool "beware of flash flooding" signs, and is more scenic. Oh, and I've never seen a burro in burro wash, but I have seen Bighorn in Bighorn Cove. If you haven't been, you should go.
Comments, additions, or complaints?