Alright so on page 86 of the Guide book when disgussing Soul Gems:
Petty Soul Gem: Can hold creature souls below lvl 4 so I guess a petty soul is lvl 1-4
Lesser Soul Gem Can hold creature souls below lvl 16 so I'm assuming a Lesser soul is lvl 5-16
Common Soul gem can hold creature souls below lvl 28 so that might make it 17-28
Greater Soul Gem can hold up to lvl 38 so lvls between 29 and 38
So therefore Grand souls are any creature with a base lvl of 38-39 and above.
So cross referencing this with the Bestary begining on page 101 excluding humanoids, that leads to the following being grand souls:
Mammoth
Elder and Ancient Dragons
Draugr Deathlord
Draugr Death Overlord ((the one with ebony weapon not ancient Nord Weapon))
Dragon Priest
Falmer Shadowmaster spellsword/warrior((assuming these are creatures and not humanoids))
Shadowmere ((but not recommended))
However you can't soul trap dragons and Shadowmere takes roughly 30 ingame days to respawn where she died
Also I would like to point out there are two types of deathlord. One has ancient weapon and dies fast and gives greater soul, the other is much harder to kill and comes with an ebony weapon and has grand soul.
Mammoths respawn the quickest especially around the giants camps in whiterun hold and the Giants are a great source of Greater Souls
::SLAUGHTERFISH::
Many of you, myself included, are upset since Bethesda decided that removing any way to attack underwater or activate a spell ((even waterbreathing)) to the point you can only rely on potions/enchanted gear and swimming reals MUST be a good idea on their part, I have found a trick around this.
Before you go too deep into water to the point you start swimming Simply activate a Flame/Frost/Lightning Cloak and swim near that annoying toothy fish. They die quick. This way you don't have to lure them to land just to bash their skulls in. This is the -ONLY- quick way to kill them.
::Disabling repeatable Traps::
This trick only works on those traps that are activated by pressure plates and are repeated such as Swining Spikey Gate and a log to the face from above.
Simply drop anything that you concider trash and manever it so it sits on the pressure plate. The trap will activate once because the pressure plate went down but since there is now an item on it, it won't move.
On Swinging Gate Traps I recomend putting a sword or a dagger, something thin that the gate goes right over without pushing it aside ((such as dead bodies or armor. You can also try garnets or other gems.
This is espeically useful if one of your dumb followers likes to run over the same pressure plate time and time again only to be nailed and then flown halfway across the room. Funny to watch but slows down dungeon proggress.


)) the second is Fallion, the redguard master conjurer that many people of Morthal do not like.