One mod that the newbs haven't tapped into yet, (and feel free to list it in your upgrades) is the reduction of air pressure in the tires for better traction.
Actually works good, at least as I watched Dustin rock crawl. As to future mod lists: Rebuild Engine, tranny, wiring (working on those now), Bronco work, then 46 work. Major mods (undecided) to all but the Cougar.