Remmington R870MCS is my fav with nice spread makes it easy to hit close up chaos combat,
the ksg is a shortranged snipercanon, fires a single slug and have little longer range than other shotties.
and the other two are more or less pray n spray,
S12 pump semi-auto 10shots before reload.
M1216 three tubes with 4 fullauto shots in each.
pretty long reload time on all of them but havent yet
felt forced to go quickmags.

i use laser and longbarrel on all my shotties, exept on the ksg i sometimes use red dot instead of laser.

Perk1 greed lightwigth and flakjacket
Perk2 scavenger
Perk3 tacmask or dext.

C4 is always nice to clear roons before enter aswell

 

Considering the subforum this is in, I think he's asking about shotguns from the first Black Ops.

They're not very good in that game, but they can still be quite fun.
I prefer the SPAS-12 Suppressor. The suppressor doesn't decrease range at all, so it basically hides you from the radar while firing for free.
For first perk, you could go stealthy and use Ghost, or take Lightweight to run around faster.
For second perk, Steady Aim is useful for tightening your spread while hipfiring. Sleight of Hand is always good too, but the SPAS has a pretty good magazine size.
Third perk I would recommend Marathon if you have it Pro. Unlimited sprinting will help you close gaps and get into close range areas where you will perform better with ease.
I remember I used to run with a smoke grenade as well. It's pretty useful if you want to get past a long sightline without being targeted.

 

1 Stakeout, steady aim pro, still sucks as it has only 4 shells. 2 Then spas silenced, although it needs a holographic site, the irons on it are awful.

Thats your lot, 3 for a troll then i would say sleight of hand olympia lightweight.

The dual weild ones are silly looking and have ridonkulous pellet spread.

 

Spas 12 with silencer with ghost steady aim and marathon
Stakeout with grip lightweight sleight of hand(since it's always better to ADS with it) and marathon
third one is shit...
You can watch XboxAhoy's weapon guides videos, it's about the same as what i've said, he is really good!

 

If you want to get good k/d's using shotties and if you have decent gaming headphones and all pro perks, then try this.

Ghost
Sleight of hand
Ninja
Shotgun of choice

Sound whoring in BO1 is amazingly effective with ninja pro and a good headset. Hearing where enemies are helps you keep engagements within range of the shotguns. Using a motion sensor with those perks can allow you to control entire buildings and get 8,9 and 11 killstreaks regularly. Or set the killstreaks low, use the other suggestions and run and gun that shotty and piss people off.

 

I wouldn't use a silencer on the shotgun as some suggest, it takes away range which can be crucial for kills sometimes. You need to move fast with them, wait behind walls and then storm into rooms with shotguns. Avoid shootouts in large open area's, as you're at a disadvantage.

 

You obviously haven't used the spas12 very much. That gun needs the suppressor due to it being semi-auto with little range already. Blasting off 4 or 5 fast shots won't help you to survive as the whole other team will immediately know where you are and what gun your using. I regularly get bb, cg and dogs with the spas, but only when I suppress it and work the map properly. Each shotgun has an attachment it works best with and the spas works best with the suppressor.

 

SPAS-12 for Black Ops 1 doesn't lose any range when you put on the suppressor, there is literally no reason not to use it.