Human body parts. All I need is an appendix (you'd think it'd be easy since NO ONE needs it anymore).
But seriously, I like to collect nature. Like for instance I like to collect sand, water, shells, and flowers from beaches across the globe and stick them in a nice looking glass bottle. This may seem really gay, but I like to take a part of it with me, ya know?
I was in South Africa last October and while I was there, I went to Cape Point. This is where the Indian ocean and Atlantic ocean meet. There I was able to collect two different types of ocean within the same hour. You could really tell the difference with the Indian being warm and greener, while the Atlantic was colder and bluer. I'm almost positive I'm the only one in the world with a bottle filled with two different oceans.