Or, I'd go to where the Founders were debating the Bill of Rights, make up some story about where I'd come from and that we'd tried the same thing, but we "overestimated politicians' honor", and the system failed, and that they were about to do the same thing. I'd do my best to make sure they were much more explicit and detailed in laying out restrictions on Federal power. As far as a gun goes, I'd probably take something not too far beyond them, maybe a black powder cartridge bolt action, just to remind them to expicitly cover tecnological advances.