Uncommonplace items you do own...

[tordis]

A set of D&D handbooks and a huge bag of dice

 

[BrumJim]

A volcanic bomb, picked from the slopes of Mount Etna. (Good job they didn't ask me what it was at airport security)
A tooth from a buffalo. Picked from its jaw, and with remnants of its last meal in the ridges.
A roller bearing that is square - pulled from the sump of a failed gearbox. And by square, I mean square, as in 4 equal sides with 90° angles between adjacent ones.

 

[Rhythm Thief]

I have some First World War bullets and barbed wire, and a bit of hand grenade casing, in a jar somewhere.

 

[Cranky]

A poster-sized, framed photograph of Junior Walker, taken by my mate at the Mercia Sporting Club, Coventry in 1988. It's so clear that you can read the engraved writing on his sax mouthpiece.

It was the best gig I've ever attended, bar none.

 

[porteous]

Two 24 volt aircraft landing lights. I have no idea why!

 

[andrew-the-tortoise]

Matchbox holder made from a WW1 brass shell casing.

A money box made from a grenade.

 

[peanut]

I have the remains of a Flying Fortress aircraft crew kit my Father's Brother brought home on leave. (he traded it for a gun with one of the bomber crew)
The Pilot's sheepskin trousers were cut up and made into various things by my Aunties due to rationing .
Still have the goggles and sheepskin bomber jacket and emergency life-raft compass and matches /tinder box

I suppose I should bequeath this stuff to a Museum eventually but I love wearing the jacket and goggles on my 1966 BSA Spitfire

 

[Mortiroloboy]

Bradley Wiggins bidon, discarded in mrs M's direction at the end of stage 2 at lasts years ToB.

 

[Mortiroloboy]

Two 24 volt aircraft landing lights. I have no idea why!

I do, you're a decendant of a famous WW1 souvenir hunter, it must be in the genes.