Sand from various locations around the world that I visit.

I collect a LOT of stuff, but two of my biggest current collections would be Salt & Pepper shakers (the only collection my wife and I have started together) and books.

I've also got a modest selection of locally made cranberry glass, stamps, hats, nut crackers, records, magic/magician paraphenelia, moustache/shaving related items, and mid-century barware....to name a few.

fabric. I am also collecting fabric from my daughters beautiful dresses so I can someday make a quilt out of them. Yay

Blades I guess. I have a lot and can't throw one away no matter how cheap (well actually once). Dunno if that counts as actively collecting..

Dead hookers. That's more of a WK answer.

***

Buddhas, I would have to say. I don't have alot of them, but the ones that make up my little "shrine" that I have mean alot to me. Each one was given to me by someone special and even when I was down to one car load of possessions as I bounced from house to house, I always kept my Buddhas with me.

Also books, but who doesn't?

Old friends who are homeless or jobless. I usually have some project they can do to get them back on their feet and on to the next sweet spot.

Also, I collect unique seashells.

What an awesome idea!

But you might want to make one for each to prevent WWIII after you croak lol.
I have a nice collection of these too. They're just good energy - period.

Old Mutoscope cards.

Porn.

Most people would say I collect comic books, I like to say I read comic books.
I do collect Comic book related things though.

Also DVDs, and now that I've got a turn table I've just started to collect records.