The only thing missing would be some Scarlex Wound Dressing (mine is still good) and some Betadine Surgical Scrub (also still good). I buy my equine shampoo, saddle soap/conditioner, and dewormers online.
I buy my stall pellets twice a year at Home Depot or Tractor Supply by the pallet, so those don't really fit in my trunk. And while my boys eat alfalfa and/or cubes, my barn owner takes care of ordering those.
I know I tend to keep things simple, but my boys are healthy and fit. They just don't need anything else. And my while my feed store has a few tack related items, it's mostly just a feed store. In some ways, that's better. If they were a true tack store, my monthly bill would be a whole lot higher!
So what's in your trunk after a visit to the feed store?