
Any item of clothing in white.
A cap on a toothpaste tube, usually lost the first time they use it. For that matter, toothpaste anyway - do they really use it in the 3 seconds they take to brush?
Clean towels - they end up on the floor anyway.
Trash can - I'm pretty sure my kids have no idea we even own one, given the wrappers on the floor.
Dog treats - she's pretty busy eating what they are leaving under their beds so she has no interest in "good for her" dog treats.
Brakes - I don't think my boys think they exist on their bikes.

Water - specifically bathwater. My boys tell me they'll just dust off.
A toolset - again, the more pieces to the set, the quicker they disappear in your home.
The remote - you'll never find that one again.
Any other useless stuff you'll add to the list?