"must do" rides? I don't know. Here are a few good ones that I like.
1. Vegas to Caliente for lunch via Corn Creek, Alamo rd, Silverstate trails, Elgin, Mormon Pass.
2. Vegas to Primm via Cottonwood, Goodsprings, Sandy Valley, Jean.
3. Valley of Fire. I have only done this one once and don't recall the route. It is a very nice scenic area. I am sure someone has tracks.
I have tracks for the first 2 and could email them to you if you are interested.