I've got a few.
A dogfish preserved in a jar (a dogfish is a small shark)
A Queen Conch shell
A glitter covered dragon statuette
A small alligator skull with fake skin and red marbles for eyes
An enormous bolt which I keep inside an equally enormous tape dispenser, both were found in a mysterious trash can along with an assortment of cables (including a 20 foot ethernet cable, a component extension cable, and an adapter to plug a cell phone into a phone line) and a rather nice speaker. This trash can was buried deep within the Middle School Band's storage closet and I was able to get it for free when I helped my band teacher clean that closet out.
A Chinese knot (a cool-looking knot that is literally impossible to untie without breaking the string) that a foreign exchange student gave to me at Christmas
And a hammer rock (no joke, a tool from the stone-age) that me and my brother found about ten years ago. I'm currently using it to prop up some books.
And that's just in this room, there's also things like a feather collection that we keep on a door-jam and a small Entei toy that was placed on a shoulder high shelf long ago and has since become an integral part of that room's decor.