I think I can pretty much speak for everyone when I say that we all have a favorite past-time in our lives. Whether you've been collecting baseball cards since you were ten, or snow globes since you were 11. It's something different for everyone.
For me, my collecting started when I was four or five, and it happened to be Legos. Yes, those little plastic pieces that lie around and are oh so painful to step on. Since then it has become more of a hobby, collecting old sets, rebuilding the sets I had back in the 1990's and so on.
At the top of my fondness for Legos, trains. I center my Lego collection around trains no matter what.
Now, not everyone might think this is a normal hobby for an 18 year-old young-man, but then, what is normal?