Shotgun for deer...
I personally haven't shot a deer with a shotgun, But...
Last year my buddy came out to the house to go hunting. It had been raining so I told him that he could set in the barn and hunt out of it...since I had already gotten a deer from there. So anyway.. he used a Mossberg 835 Ulti-Mag with a turkey choke and 3 1/2" 00 buckshot. He shot the deer at 50 yards..he did shoot it twice. But the 2 shot caused it to do a back flip. Nice buck. So I think a shotgun, properly patterned, with a well choked tube (full, x-tra full, or turkey x-tra full) will do the job. If you get a good shot. But I would stay 50 yards or less.
If I were to hunt with a shotgun though, I would use a fully rifled barrel with one of the Winchester Supreme Slugs or the Remington Copper Solid Slug. And a properly sighted scope. (if it is legal to use slugs where you hunt).
But I know buckshot is lethal. You just have to know your limits, how the gun patterns. And be a good tracker since buckshot deer do not bleed out like a deer shot with a slug or rifle.
Good Luck