#1, for me, is a heavy duty rubber floor mat. Unlike spray-on bed liners nothing slides on these mats. Same reason I don't file the plastic full bed liners. About once a year I take out the liner and wash the debris out of the bed
I've had multiple trucks. Some have gone to over 250K miles. They all have gotten to haul just about anything. Stuff for Junk yard, (metal and wood), Wood for fireplace, Riding Lawn mowers, Rock, Dirt, Bricks.....Just about anything. My experience has shown me that the rest of the truck usually rusts out about the same time as the truck bed. I simply do not worry about paint scrapes on the inside of the bed or tailgate. It is, after all, a truck
I'm a big fan of ratcheting tie downs in multiple weight capacities and lengths.