Like in F3, i was kinda mad to try to get all the bobbleheads and find that one was in Raven Rock, and you can't access the location again.

Are there any items, guns, armor, etc. that you only have one chance to get?

You have two chances to get Maria; but I don't know why anyone would help Benny escape.

The snowglobes can be obtained at anytime, however you can't display them or get caps for them if you kill House.