I have always collected and built both cars and military aircraft. I have a huge stash of drag and showrods, and a smattering of racing and supercars. I have virtually every military aircraft- planes and helicopters- ever kitted in either injection, resin, or vacuform, in 1/72.
I love kitbashing drag and showrods. On the creative side of aircraft, I don't kitbash but I build a lot of X-planes, experimental aircraft, one-of-a-kinds, things that only made it to the drawing boards. This gets me out of the likes of the military sites, where you see the same planes all the time- everyone has a Zero, P-51, F-14, Phantom, etc., etc. pretty common. I love building the uncommon. I love armor, but I always knew that would be one subject too many, so I content myself with my collection of ROCO minitanks. I never got into ships or figures, though I did a couple as a kid. I'm not into most sci-fi subjects, like Star Wars or Star Trek, but I never could resist flying saucers, so I have probably more than a dozen- from Lost In Space, The Invaders, Earth VS. The Flying Saucers, The Day The Earth Stood Still, The Thing, War of The Worlds (ok, not really a saucer, but they ARE really cool!), Flying Sub (ok, also not a saucer), Forbidden Planet, and a few lesser knowns.
Most of my friends here locally build models, we all have different tastes; one builds figures, another sci-fi, another big rigs, his brother, large scale dinosaurs and armor. As long as you're having fun, it's all good. The sad thing is, all of us are over 60- and NONE of our kids build models. NONE. And we tried. Video gaming- never could get interested in that.
I'm just not a stickler for rivet counting, I'm not aiming for professional replicas. I want a nice, clean build that I'm happy with on my shelf.
Building models take me back to being a kid again, having fun; I'm glad I never stopped.