Ti pots, mugs, utensils. I go for aluminum pots and plastic mugs and utensils.
Knife with a blade longer than 1.5″
Water filter systems. I go with Aquamira.
More than one of any clothing item except socks.
Rain shell and pants. Wore them for decades but went back to ponchos/capes after getting caught in a Sierra Nevada thunderstorm at altitude with three other men. Horizontal rain, then hail and sleet, lightning strikes less than a second away. I had brought a poncho to save weight, they all had shells and pants. To my great surprise, I was comfortable but they were all borderline hypothermic by the time we got back down to the cars. Just started using the SMD Gatewood Cape as poncho, pack cover and tent.
More than one celebratory shot of booze. Too heavy. I go with…wait…um, never mind.
Headlamp that weighs more than 2 ounces or cost more then $20.
White gas or kerosene stoves. Period.
Chair or stool.