I don't think I could condense 25 years of camping into one post but here's what has stood out to me.
Down sleeping bag at least 10 degrees colder then the coldest I expect to sleep in.
Sleeping bag liner.
Thermarest 3/4 deluxe over a ridge rest.
For years I had a single wall Garuda Kaja tent. Now I have a Kingdom 6 family tent.
Compression stuff sacks
Kung Fu shoes for camp shoes unless it's really wet
Non stick pans, that have been painted black on the bottom of the outside
Scraper and cut down sponge and castille(sp?) soap
Two ways to start fires and something to eat that doesn't need to be cooked in addition to the normal rations of food.
Pillow stuff sack, it's made of fleece on the inside and nylon on the outside, stuff it with my jacket and it's a great pillow.
On vacation for a spell