I'll add/support a few items, and then qualify/defend a few off the OPs list...
0. Anything at FULL PRICE. Except for gear you need urgently, or consumables like fuel, you should NEVER pay full price for anything at REI or comparable stores. Every single piece of gear from retail outlets will be available 20-30% off if you're willing to wait a few weeks. Most of it will be available 40-60% off if you're willing to wait longer, and some of it will be available in the 60-90% off range if you're really patient.
1. "Deluxe" mattresses. I went camping this summer with a friend who showed up with a sleeping pad that was 5+ pounds. If I'd known in advance, I would have loaned him a lighter pad -- any pad. He was a great sport about it, but it amazed me he carried that thing, albeit only on a short overnight hike. (A group of us were taking my youngest sister on her first overnight trip).
2. Compression sacks. The only thing I've found these useful for is compressing synthetic sleeping bags, back when I was carrying a 4# synthetic on the trail, but if that's all you have as a sleeping bag, a compression sack can be the only way to pack it.
3. I'll agree with the pack covers. Most pack covers weigh the same or more than a poncho tarp (or even a drug store poncho, large enough to go over a backpack), with far less functionality.
4. Heavy hiking boots. Sure, some people need extra ankle support, but no one needs boots that weigh 3# each, no matter how much Leather, GoreTex and Vibram are used to make them.
5. Camp chairs -- it's one thing to bring a foam mat to sit on, or some sort of lightweight rig to turn your sleeping pad into a camp lounger, but those "camp chairs" (and camp tables, etc...) are unreal. Car camping, sure... backpacking, uh, no.
6. Footprints -- true footprints can be $50 for a lot of tents, and they are great if you are planning on doing an ultralight pitch, and leaving the tent inner at home on a double-wall design, but unless you are doing a simple pitch, they are expensive and overkill. Most people using traditional double-wall tents will never go without the whole package.
1. First Aid kits -- I love the Adventure Medical and other similar kits. Don't ever buy them at full price, but they frequently go on clearance 50-75% off, and you can get a full kit for a few dollars, and its the easiest way to get a hold of useful, but seldom used, items like tiny foil packages of neosporin... Sure, don't carry the whole kit with you, but it's great to have that many options on hand for a build-your-own first aid kit, and not have to worry about tracking down lots of tiny bottles and ziploc bags...
2. Knives. I know it's not ultralight, but I just feel better having a good knife with me in the backcountry. Even if it's not needed, its a 3 or 4-oz security blanket. Granted, on a solo trip, I'll take something like a mini SAK, but if I'm sharing gear with anyone, lightening the load, I'll use some of the savings on a knife.