LeMat revolver. I'd like to see a good exact reproduction of the original be made (9 rounds of .42, and one round of 16 GA, or 18 GA, or 20 GA (I couldn't get one answer for what gauge was used)), and I'd like to see a modern version made.
I'm thinking of something along the lines of 7-9 rounds of .357, and 1 round of .410. for a small version, and 7-8 rounds of .44 mag and 1 round of 20 GA for a large version.

(Yes, they would way a TON, but you would probably want them to because of the kick.