Smoking gun

We found a smoking gun.

We found a smoking gun.

— Brooklyn Nine-Nine S5E15

But this is the smoking gun I've been waiting for.

But this is the smoking gun I've been waiting for.

— Gossip Girl S2E17

Now I could tell you that I've got the canceled checks or the wire transfer or whatever smoking gun that exists--I don't.

Now I could tell you that I've got the canceled checks or the wire transfer or whatever smoking gun that exists--I don't.

— Suits S1E1

Then, while they were looking for a smoking gun in that room...

Then, while they were looking for a smoking gun in that room...

— The Wolf of Wall Street

Not quite a smoking gun, but at least we know the perp drove a truck.

Not quite a smoking gun, but at least we know the perp drove a truck.

— Young Sheldon S6E20