I’ll start.

Strangely enough it wasn’t my metal match once I got to thinking about it.
Turned out to be the bandanas. 101+ uses, light and cheap, there isn’t a day I don’t pull out and use more than one.

(FYI I’m considering a shemagh nothing but an oversized bandana.)

Again after much thought, the first item ended up being a 1.5qt ‘billy pot’.
Boiling water for a spot of tea, cooking dinner, protecting breakables, impromptu digging, carrying foraged grub, holding a hot rock to warm the sleeping bag, it gets used a lot.

Second: My old rubberized poncho.
Keeping the rain and snow off, warmer than the thin cheap new ones, making a lean to, making a flotation pack, camoflage when hunting, a seat when its not raining but the ground is wet, and so on. I’ve tried others but keep coming back to the old one despite it getting very old and needing replacement.

Third: This was actually the hardest one as there’s a number of things that came to mind, such as the shingling hammer, the compass (spare), and such.
But it came down to what i use the most, what gets replaced constantly, 550 paracord gets the nod.
Seems like I add another 100′ after every time out.

Now my BOB is also my GHB as well as my light backpacking pack and hunting pack, so it does see more than a little use.

As to the unusual?
A tea cup.
My grandfather carried a similar one through WWII and Korea, just for that touch of civilization in the midst of chaos.