What Do You Collect?

I think anyone who frequents garage sales and/or thrift stores looking for bargains eventually ends up buying things they just think are cool or too cheap to pass up. Then comes  another sale, and another purchase, and then slowly a collection is born. So we end up with a number of collections that we never expected to start. Most of my collections are inexpensive but lots of fun, although I will spend more if I find a special piece. Presently my collections consist of brown drip pottery, Niagara Falls postcards and memorabilia, postcards of Buffalo NY and US caves and caverns, Nemadji pottery, Campbell's Soup advertising, coffee mugs, cookbooks, Pfaltzgraff Yorktowne dinnerware, teapots and tea bag holders. In the past I have collected medical almanacs, Victorian trade cards, vintage planters, chalkware, vintage photos, advertising tins, and travel souvenirs. I'm sure there are more that I have forgotten. But collections come and collections go. I enjoy them for a while and often end up turning them over for others to appreciate. Who knows what I will find next?
What are some of your favorite collections?