I collect skills and knowledge. It's the only explanation I can come up with for the variety of hobbies I've had in my life. Woodworking, DIY home improvement, fly tying, firearms and handloading, photography, calligraphy, lapidary, silversmithing, leatherworking, model rocketry, RC flying, and many, many others...even taxidermy.
As for collecting real things, I wouldn't really call myself a collector. That is, I don't collect them as an activity unto itself. I have a collection of guns but I wouldn't say that I'm a gun collector. No antiques or RAHTF models. Just my EDCs and other shooters. Similarly, I also have a collection of woodworking tools but the emphasis is on "working." You might say they make dust rather than sit around collecting it. I have a small selection of Citizen watches but I wouldn't call four a collection.
Now that I think about, I did collect unit and system patches when I was in the USAF but I have only one left to speak of.