Probably the plastic measuring jug that I use as an intermediary between the sink and the electric kettle. The kettle doesn't have an external gauge, so it's useful for putting specific amounts of water into it. The jug used to belong to my grandmother.

I want to say that I'd probably miss it more for its usefulness than its sentimental value, but don't really want to force myself to actually decide for sure, nor damage it to find out.

That said, I've proven pretty sentimental about most things, regardless of their origin, so I'd definitely have some level of distress about it.