Lots of "collecting" hobbies on here! Personally I prefer more interactive hobbies, usually something that involves my kids who are my world!
My favorite hobby is definitely my RC trucks. I'm not talking about little off the shelf from wal-mart trucks... I'm talking about 55 mph 1/10th scale waterproof offroad madness! I even built a figure 8 track in my yard so my daughter, my neighbor, and myself can all race our trucks. Started out with just 1 as a "family" gift for Christmas. My daughter started driving and fell in love, so this year we got her one of her own for Christmas. My 4yr. old son also drives mine, I just turn the throttle adjustment back some for him. They are a little pricey to get started, but this is a hobby, so compared to some other hobbies, it's really not that bad. 600$ will get you a real solid truck/charger setup and really besides replacing small plastic parts as they break there isn't a whole lot required on top of that.
The fun of the hobby for me though, is not only driving the little bad boys, but in the hop ups and customizing it. I got an unpainted body to replace my stock body, painted it myself and made it more of "my own" truck! I've put tons of other upgrades to aluminum parts on it too. The best upgrade yet (maybe) is in the works right now, as a friend of mine who owns a fabricating business, is working on making me a new frame (chassis) for it that will lower the center of gravity making it harder to roll over. It's also lighter than the stock chassis so it should go faster, and corner faster without flipping!
Anyone interested in checking them out just go search youtube for Slash VXL or Rustler VXL (these are the brushless motor models. I have a slash my daughters is a Rustler
) You'll see some of the madness that I'm talking about with these trucks! They are near bullet proof! haha.