I would prefer a double rifle for follow up on cats, and all other game for that matter.

However I did see a double bbl shotgun that was fitted with a spike bayonet fron as SKS. The owners theory was if the Leopard made it past both bbls the bayonet might keep the leopard off his body while others "filled him full of lead".
He felt if he could "stick" the leopard he could divert his jump and possibly pin him to the ground.