What fascinates you about guns?
Everything.
Actually, many of humankind's accomplishments fascinate me.
I find most anything and everything interesting.
I find it amazing the gargantuan skyscrapers we can build.
The great pyramids.
I constantly ponder how amazing computers are.
I'd have to say the one thing about guns that fascinates me the most is ammunition; the incredible precision that is demanded.
I dunno 'bout you, and maybe its just 'cause I don't shoot as much as some people here, but I've never had a bad cartridge. I mean like a round that just wouldn't fire or something.
(Well, maybe I've had one or two, but only one or two...still pretty impressive)
Anyhow, I just find it amazing that ammo will 99.99999999999% of the time, always go "boom."
Oh, and tires too....those are amazing too....the stresses they have to hold up to...