[alexbock]

You do not need a Federal Firearms License nor registration as a Special Occupation Taxpayer to purchase fully automatic weapons that had been registered in the National Firearms Registration and Transfer Record prior to 1986. All of the other items you mentioned are legal to purchase or privately manufacture as long as you comply with the National Firearms Act by registering and paying a tax on them (usually $200). I don't think there is any weapon which is outright illegal for a civilian to own federally in the United States except a nuclear weapon as plutonium and enriched uranium are restricted by the Nuclear Regulatory Commission.

[philipkglass]

There may not be a formal list of civilian-prohibited weapons but I'd be astonished if you can find someone who has a Title II license to own a MANPADS or even an ATGM.