- Camelback systems - These are heavy, cumbersome, hard to fill (relative to a bottle), hard to pack in/out of a full bag, horrible in the cold where they freeze up, bad amid bushwhacking, and make it hard to know how much of the liquid you've got left or have consumed. I'd only bring one if there's simply a long casual summertime hike into a basecamp area, from which I'd be doing short climbs. (Wind Rivers, Pasayten...)
- Quick Links - These get rusted shut and are hard to remove from the bolt that one uses them to bail from. Just bail from a wiregate with a sticky gate. It's far easier and doesn't require you carrying around a special "just in case" gizmo for months or years beforehand.
- Rap Rings - See above. When rapping from new cord or webbing, you don't need to leave any metal at all.
- 1" Webbing - Use ~5mm cord
- Nut Tool - For long routes or difficulty backcountry rock climbs at or near my limit, I often wont bring a nut tool. I don't place or fall onto too many small wires amid this kind of climbing, and don't mind having to leave the random piece behind if needed.
- Maps - Don't bring a paper map, download a super cheap phone map APP like "Topo Maps" - It lets you download all the maps for the area where you'll be, then you can put your phone in airplane mode, and the internal GPS will show you just where you are on the map.
- Water Pumping Gizmos - Drink from small feeder streams or tributary sources that are running from snow patches or terrain not crossed by popular trails. You'll be fine.
- Dishes (on serious multiday climbs) - Just eat a freeze dried meal from a durable pouch on day1, and then use the bottom half of that bag/pouch for future meals.
- Knife - It's easy to cut webbing or cord with an ice axe, lighter, cam lobe, or small rock. Just hold the piece taut and hack away.
- Pack Frame - Use your foam or inflatable pad and fold it into the frame sleeze.
- Hexes, Medium-Large Tricams, Cordelletes, Padded gear slings, Large Lockers, Snowshoes, Gaiters - Nerd Alert!
I recently spoke at the Boeing Alpine Club in Seattle, which is a really supportive and enthusiastic group of climbers with a wide range of abilities and experience levels. It was fun to chat with the group, and one of the topics I was thinking about is the variety of items that I don't typically use or carry, but which many people bring along.