Wrong

Nechrochasm: only one means of acquiring it, drop rate minimal. Rarity confirmed Thunderlord: never been sold by Xur, infrequent drop. Rarity confirmed Thorn: most difficult bounty weapon to acquire, many PvE players don't even try. Rarity confirmed. Ghorn: perhaps not as rare since Xur sold it last, but still more than most, infrequent drop. Rarity confirmed. Vex (should have been the 5th, not sure why I forgot about it): Only one means of acquiring it, drop rate minimal. Rarity confirmed. Ps exclusives were not taken into consideration.

Thunderlord, hardlight, montecarlo, hawkmoon, and 4th horseman. Thunderlord and hardlight have never been sold, ps exclusives wont be sold until fall of this year meaning that they are unavailable to half the community plus havent been sold. Vex and necrochasm are the easiest exotics to get because there is a sure way to get both through repetition. Ghorn has been sold once so surely some people bought it, and thorn bounty is piss easy to do if it drops.

I forgot about Hardlight. I wasn't including the ps exclusives as I play on Xbox and based my list off of what I've seen.