-Get a clear elbow (prefferably the Valterra with the spray) for dumping and some sort of tank flushing item (wand, Tornado system, or the spray nozzle on the Valterra works great for me).
-Try to get the dealer to change the Touch Audio with the Jensen unit. It is much better and actually works. They did mine before I took delivery.
-Max Air vents. I still need to get these, but they are good to have for a rainy day.
-19-26" TV like cstover said. Especially if you have kids. Look at Wal-Mart or Target for a good cheap one.
-Water filter for the FW city supply line. Just need one that you can put garden hose ends on. I use the Camco in line one for $18 at Wal-Mart.
-MEMORY FOAM MATTRESS TOPPER (big letters for a reason) at least a 2.5" one. We got ours at Sams for $100 and it makes a world of difference.
TV: '06 Ram 1500 SLT QCSB Hemi 4x4
TT: '12 Grey Wolf 27BHKS
Tow Acc: Tekonsha P3 BC, Curt round bar WDH w/sway control, CIPA custom fit tow mirrors