Below are hot links w/ info about 12 gauge ammunition for defensive purposes.  Below that is a list of Commercial or LEO packaged cartridges that are suitable for self defense.  

Link to AR15.com ammo oracle self defense ammo list.  Shotgun ammo is at the bottom & is brief & is only for 12 gauge.  The beginning gives an explanation of the importance of penetration in any small arm projectile. HERE.

Link to Article about defensive shotgun ammo on firearmstactical.com HERE.

Link to Old Painless Box of truth site for actual ballistics testing HERE.

Link to a fantastic thread on shotgun world.com that has pics of gelatin tests of all sorts of shotgun ammo.  Not for dial up.  HERE

Link to Tactical Works.ca that seems to be source of pics in the link above.  Also, there are pics of terminal wounds in various dissected game.  HERE

Link to Squeaky's Gun-Deals.com site that can show you instantly the best delivered price on ammo by caliber.  HERE

20 gauge:
#2 or #3 lead buckshot is the biggest available. (#2 is larger than #3) The #3 loads may be better for those who are recoil sensitive but should only be chosen over #2 if absolutely necessary.  Plated shot very preferable as w/ shot this small you need every thing you can to improve penetration.  Neither Remington nor Winchester make #2 or #3 plated lead 20 guage cartridges.  Federal makes both in their Premium "Vital-Shok" line.  

20 Gauge Federal Premium Vital-Shok PLATED Lead Buckshot:
-2-3/4", 20 pellet, #3, 1175 FPS, Part# P256
-3", 18 pellet, #2, 1100 FPS, part # P258
-federal, winchester & remington make some unplated buck in #2 &/or #3

FYI: Walmart sells a Remington youth 20 gauge w/ 18" barrel & removable choke


16 Gauge:
I can only find un-plated buckshot in shot size #1 by Winchester & Federal.  Note that I haven't read any 16 gauge ballistic testing or anything.  I am just showing you the largest 16 gauge buck shot available.  
-Winchester makes Super-X, 2 3/4", un-plated,12 pellet, #1 buck, 1225 FPS, part #XB161
-Federal Power-Shok, 2 3/4", un-plated, 12 pellet, #1 buck, 1225 FPS, part #F164


12 Gauge:
12 Gauge #1 Buckshot: the International Wound Ballistics Association argues that all other thing being equal #1 buckshot is the best b/c compared to 9 pellet 00 buck 16 pellet #1 has the ability to produce "over 30% more potentially effective wound trauma."  Additionally, it is the less likely to over-penetrate or penetrate barriers than 0 or 00 buckshot.  Since it is less likely to overpenetrate, plated would be preferable.  Currently I only see non-plated offerings from Remington & Winchester.  There are no Flite Control loads w/ #1 available, so pattern sizes will be undesirably large w/o a choke.  Federal does not offer any at all.  
-Winchester Super X, 2-3/4" 16 pellet 1250 FPS, Part #XB121, $3.53/box/50 boxes
-Winchester Super X, 3" 24 pellet!, 1040 FPS,
-Remington Express, 1250 FPS, Part #12B1, $3.53/box/50 boxes


12 Gauge Low Recoil 00 Buck Shot: Low recoil loads will often not cycle reliable in auto-loading shotguns but offer more comfort & faster follow up shots in pump shotguns.  

Commercial Packaged:
-Remington "Expressed Managed Recoil", non plated, 8 Pellet, 2 3/4", 00 Buck, 1200 FPS.  Rem part #RL12BK00
-Winchester Winlite, 8 or 9?, plated?, 1125 FPS, part #: WL1200
-Federal "Power-Shock", non-plated, 9 Pellet, 1140 FPS, part #H132
-Fiocchi Premium Nickel Plated, 8 or 9 pellet?, 1150 FPS, part #12LE00BK
-Federal Power-Shok Low Recoil, non plated, 9 pellet, 00 Buck, 1140 FPS, #H132

LE packaged:
-Winchester Ranger, 9 pellet, 25 rd box, non-plated, 1145 FPS, #RA1200
-Winchester Ranger, 9 pellet, 5 rd box, non-plated, 1145 FPS, #RA12005
-Winchester Ranger, 8 pellet, 25 rd box, non-plated, 1145 FPS, #RA12008
-Winchester Ranger, 8 pellet,  5 rd box, non-plated, 1145 FPS, #RA120085
-Hornady TAP Blue Hull, 8 pellet, non plated, 1100 FPS: Part #8628.
-Remington hardened, 8 pellet, ? FPS, #RR128B00
-Remington hardened, 9 pellet, ? FPS, #RR12BK
-Fiocchi Premium Nickel Plated, 8 or 9 pellet?, 1150 FPS, part #12LE00BK
-Federal has several that are covered below in the Flite Control Section


12 Gauge Standard Power 00 Buck: If you are shooting an auto, any one will do really.  Plated or hardened pellets will pattern & penetrate better but are a little more likely to overpenetrate.  There are various loads in Commercial & LE packaging in various length & pellet counts.  Some Remington LE packaged ammo is water proof.  The Federal Flite Control, disussed next, will have the best patterns from a cylinder bore shotgun.


Federal Flite Control 00 Buck: Federal Premium Shot shell ammo w/ Flite Control wad makes the best patterns when shot out of cylinder bore barrel.  The proprietary Flite Control Wad is really unlike anything else.  People report X' patterns @ Y yards w/ 18" Cylinder bore barrels.  They make Low & regular recoil loads in LE packaged ammo & regular loads in commercial ammo.  Commercial ammo w/ the "PFC" prefix on the part number is Premium Flite Control ammo.  The "Precision Buckshot" features unique wad that actually retains the shot the entire time in flight until it hits something.  That one seems less safe in terms of barrier penetration but would be the ultimate in a tight pattern!  Federal's "partner company" Speer also has a Lawman offereing w/ the Flite Control Wad.

Commercial Packaged:
-PFC154: Premium Vital Shok, 2-3/4", plated, 9 pellet, 1325 FPS
-PFC157: Premium Vital Shok, 3", plated, 12 pellet, 1325 FPS

LE Packaged:
-LE127:Standard recoil, 2-3/4", plated, 9 pellet, 1325 FPS (same as PFC154)
-LE132: Low Recoil, 2-3/4", plated, 9 pellet, 1145 FPS
-LE133 Low Recoil, 2-3/4", plated, 8 pellet, 1145 FPS
-LE133 00PR: "Precision Buckshot", plated, 2 3/4", 8 pellet, 1050 FPS.
-57800: Speer Lawman Buckshot, 2-3/4", plated, 8 pellet, 1145 FPS (same as Federal LE133)

Slugs:  These should almost always have sufficient penetration for two-legged deer, but again are more dangerous to everyone else.  Naturally, they are a better option at longer distances.  There are basically 2 different type of slugs.  
-Rifled Slugs (aka Foster Slugs): These are designed to be shot out of smooth boor barrels.  These slugs are designed to "swage" down to fit through choke tubes.  They may be shot out of most chokes excepting super full or specialty turkey type chokes.  However, more constrictive chokes may produce higher recoil & lead to higher amouts of slug deformation & more errant point of impact.  Brenneke brand slugs are type of foster slug that are somewhat unique in there design & materials.
-Saboted Slugs: These are intended to be shot from rifled shotguns & offer higher accuracy than shooting other types of slugs from smooth bore weapons.  

Exotic Cartridges:  There are various types of specialty type shotgun cartridges.  There are types w/ two or three slugs, two slugs tethered together, steel core darts, multiple small finned darts, flame throwing, smoke making etc.  Some of these are pretty neat & probably fun.  They are generally very expensive, compared to conventional ammo and so even if their design features were considered tactically sound, it is hard to justify their price.  Do be advised that some states have laws banning various type of exotic shotgun ammo.  

Fantasy: On Future Weapons I saw retractable fin stabilized 12 gauge round with a high explosive warhead  Thinking about it gives me a little bit of a chub

Not to endorse any particular resource, I would nonetheless also suggest a peek at http://www.tacticalshotgun.ca/ballistics_shotgun.html. There is a considerable body of gel tests at this site. A bit of caution is in order: the ballistic gelatin in several of the test cases on this site is apparently mixed a bit thin or it is on the warm side, as the calibration BB penetration is deeper than the standard. My non-scientific guess is that test load penetration is running about 20% greater than a properly calibrated block in those tests. Having said that, you can still get a decent idea of the performance of many loads, from the reliably deadly #8 birdshot, recommended by shotgun philosophers everywhere {sarcasm}, through various 00 loads and slugs.

I think the biggest surprise to me was that BB and #4 were more impressive than I expected. Again, the medium is on the mushy side, but even so, a realistic 8-10" avg for 75 BBs and 10-12" for 27 .24 cal #4's makes them more "serious" than popular discussion would indicate. Also, #1 looks like it not only has clearly sufficient penetration but also more overall tissue disruption than 00.

What I walked away with was that if you are shooting a
(1) tight-patterning load
(2) with pellet diameter of .20 or greater
(3) at typical in-home distance (under 30 feet)
you have an excellent opportunity to stop aggression with a reasonably centered hit.

My 18-18.5 in guns have all been fitted for choke tubes, which I think gives me a genuine viable #4 load option. Gives me a good excuse to bust a few caps on a fun patterning project!

[Edited to clarify a vague sentence –– sorry about that]

Winchester Ranger 9 pellet #RA1200 is unplated 1145fps.All the Hornady TAP I ever saw was unplated as well.

Tack it!

Edited.  Thanks.

XM193cure, I'll look over that info later on & see what they say.  Perhaps I'll add it some of that info to the top.  I can't argue about the validity of the FBI penetration test standard.  It seemed like they had thought it through pretty well so the 12" would give you a margin for particular circumstances that would be more ballistically challenging.  I hope that people smarter than me made it w/ good reason & perform the tests in a very controlled & consistent fashion.   I have definitely heard antidotal stories about failure of bird shot to stop people....

Any comments on differnt types of slugs.  I really don't know much about them.  I suppose my general assumption about them being sufficiently penetrating is true.

I know there are low tech rifled & foster slugs & there are high tech slugs like a saboted hydroshock slug, but it seems to me me like any of them plow through a dude & make a big hole about the same?  Is there something else that makes some slugs better than other?

Your part number for the Winchester Ranger 9 pellet is wrong.

RA1200: 9 pellet,25 round box,1145fps
RA12005: 9 pellet,5 round box,1145fps
RA12008: 8 pellet,25 round box,1145fps
RA120085: 8 pellet,5 round box,1145fps

RA12RS15: low recoil 1oz. slug,5 round box,1200fps

I agreed with everything until this point.

The flutes on "rifled slugs" are intended to swage down when passing through a choke, not to impart spin to the slug

Foster slugs ARE rifled slugs, not sabots. Foster slugs can be fired from all shotgun barrels, including barrels with a choke. You can argue that Brenneke slugs are rifled slugs, but they are able to be fired from a shotgun with a choke

*Sabot slugs are intended for rifled barrels only.


The #1 buckshot loads mentioned for their "30% more wound effectiveness", recoil like an elephant gun! Not conducive to quick follow-up shots.

For reduced penetration indoors, #4 buck is a good option.
Close-range lethality and wide patterns at such distances shouldn't be an issue.
S&B makes a 1210 FPS 21-pellet #4 buck load that would be an ideal load for indoor defensive scenarios.

For Winchester 1300, H&R single-shot and double-barrel shotguns, the Aguila Mini-Slug is a viable HD option––.72 dia, 385 grain lead slug @ 1250 FPS will put a hurtin' on any bad guy unfortunate enough to be on the receiving end of one

I will correct all the information.  

Thanks for the input everyone.  

Mike, Perhaps when it is all straight you or I can copy the correct info to a new thread & tack it.

Great list Thanks for all your work .
RLTW

Info added.  Thanks.

Okay,
I did a little work on it.  

I corrected the Ranger part numbers & added more line items.  

I added two more links, the ones to shotgunworld.com & tacticalworks.ca.  I also added a brief section on exotic ammo.  

Finally, I corrected the section about slugs. Please review it & make sure it looks alright.

I wanted to bump this and ask that it get tacked for the links in the first post. Very good information.

Mike told me to copy paste it to a new thread & he will tack it.  Thanks for for your interest.  

HERE is link to the new thread.   Let this thread die & if there is new info to add to the post you can reply in the new tacked thread & I'll update the OP from time to time.

Sub'd for later reading. Thanks.