Yes, most people who do offroading have one. It's great for communication out on the trail.
There are a ton of inexpensive options. I have a Cobra 75, which is one of the smallest options. But it has a weak speaker, so I added a cheap external speaker.
You'll want to search/post in the JK forum to see mounting options for the CB and antenna. There are a ton of different options.
My Ammo Can Console: http://www.jeepforum.com/forum/f12/yet-another-ammo-can-project-finished-1498520/
My 8.8 Swap: http://www.jeepforum.com/forum/f12/yet-another-ford-8-8-swap-extras-1565339/