Hobbies.... I've collected them through the years.
Aside from music, which is a hobby for me now.... I used to make my living in it.... but now, not so much. It's currently relegated to hobby status.
I like guns.... and have quite a few nice ones. I love all things shooting. Rifles, pistols, and shotguns.... love them all. I inherited a nice Browning Belgium A5 which turns heads at shooting events when I bring it to the line. There's always someone there who offers to buy it from me and I always smile and tell them "Thank you kindly, however, No thanks... it has sentimental value beyond it's dollar value and I'm keeping it in the family".
I studied martial arts for many years and one of the interesting aspects of our art was the use and training in weapons, specifically, the Japanese Katana. I can't afford any of the "real/authentic" Japanese swords so I have a replica blade that was actually a gift given to me by a friend. I had some collectors look at it and they said it was a nicely made replica.... not of old Japanese origin. You wouldn't want to use it in a sword fight.
Photography, motorcycles, flight simulators (as Randy mentioned, but not to the degree he's into), flying real planes with a PP license (talk about an expensive hobby...OMG!!!) , working on restoring wooden furniture from time to time, and now.... probably the most expensive one of all... A hobby farm. We're planning goats, honey bees, and a large garden. I've got a small tractor that runs and I'll be restoring to it's former glory when I get the time.
And of course... I'm very careful not to call this a hobby within earshot of my K-9 team commander....( I only made that mistake one time)..... but I'm also training my German Shepard in the fine art and skill of human remains detection. or as it is commonly called.... a Cadaver Dog. We're part of a search team that assists law enforcement and government in searches for living and deceased people when they go missing, a crime is suspected of having been committed regarding a missing person, or after a disaster such as flood, earthquake or hurricane/tornado damage to buildings that may have had people in them. That's some interesting and fascinating work. So much to learn on so many different levels from scent theory on how scent behaves under various field conditions (hot, cold, new, old, wet, dry, calm, windy, terrain, etc...) , woodcraft and wilderness survival, urban search conditions, man tracking, compass navigation, and of course, how dogs think and react and learning how to read the dog's body language to determine what the dog is trying to tell me. It's fun, and we have a great team of like minded volunteers.
Needless to say, I can easily stay busy with those things.