What unique items could become unobtainable?

After finishing The Human Error quest with the resolution that made it impossible to buy the unique equipment from Penny Fitzgerald (Destroyer's Helmet and Justice), I realized there must be unique gear that can become unobtainable after certain quests/events if not previously obtained.

I also know there is a point later in the main story quest line that will make you an enemy of some factions, which probably leads to more unobtainable gear if they aren't purchased/obtained before the respective quest is complete.

Is there a list of gear that can become unobtainable, and the quest/event that makes it unobtainable? I'd hate to find out down the line that I missed desirable unique equipment by unknowingly progressing through a quest.