Things you expect in pawn shops: jewelry, electronics, and nuclear bomb parts.
Wait, that last one isn't right. No one expects to find nuclear bomb parts in a pawn shop. But in this scene from Pawn Stars, Rick calls in an expert to assess whether the cover for a B-57 nuclear bomb is authentic.
The B-57 is a thermonuclear weapon that uses the W-44 Tsetse, a 300-ton to 10-kiloton warhead, as a primary charge that triggers a 5 to 20-kiloton secondary explosion. The weapon was tested and deployed as everything from an airburst weapon to a nuclear depth charge.
It was even deployed, but not used, on the USS America during Operation Desert Storm.
On its own, the cover for a B-57 is no more capable of being used as a weapon than a pen cap is of writing, so it's perfectly safe to buy and sell. Of course, it's also hard to find a use for nuclear bomb parts without any nuclear bombs.
See Pawn Star Rick negotiate the purchase in this clip: