Collecting firearms is like collecting planes (the woodworking kind) I don't see it. That's just me firearms are tools I've got a few and I have some that I'd never part with.
S&W 17 no dash from 1957
My three M1s I had to have three to use the stacking swivel.
Other than those I'm not into collecting.
Firearms I think are Icons; Mauser C96 that was the first viable semi-auto pistol, Browning's HiPower, Springfield Trapdoor the gun that really won the west, The M1 rifle, the greatest battle implement known to man.
For more modern ones I'd say the S&W model 39, I know Glock 17 wasn't the first but is the best known polymer framed handgun, to leave out the Armalite model 15 would be a crime.