+1 for it has to be what YOU like to shoot and enjoy owning (as a shooter or collectible piece). Your interests and tastes may change over the years as well.
For "notable weapons", I think most have been mentioned.
I have mainly focused on 9mm semi autos and 1911's with my sole interest in revolvers being Colt "snake guns". Then just recently, I have been looking more at heavy barreled/target rifles and bigger caliber revolvers. Others may prefer 40S&W as "caliber of choice" or say they won't own a Glock as part of a "collection." To me, my Glocks are another fine example of a reliable/accurate 9mm - not the best (IMHO), but certainly worthy of a place in a accumulation/collection.
I couldn't care less what others thought about my accumulation or collection of weapons (I also like knives) - they are what I like and can appreciate the work involved in searching, finding, saving, purchasing, and USING them.