Fully automatic weapons.
>To legally own a fully-automatic weapon requires three things: money, time, and an absolutely pristine criminal record
Git you some, anon.
Start your collection in a year, after your application is approved.
The infringement is in the expensive tax.
https://www.washingtonexaminer.com/its-still-legal-to-own-a-machine-gun-its-also-extremely-difficult-and-especially-expensive