I have a small pipe collection, which I gaze at longingly from time to time since I quit smoking shortly before my daughter was born. I also have a small collection of replica swords, because I like them, and replicas were all I could afford for a long time. A few Chinese style Buddhas. A couple guns... you know the usual. I don't have big collections of anything. Even with knives I'm not so much a collector as I lover of knives. I don't have a ton, just a few that I really love an use. But I love seeing other people's collections.
Actually, now that I think about it, I do have a bit of a rock collection. I like obsidian, and I have a few fossils.