I like it, and would welcome this in my game. What about a ghost or other spectral creature? You'd probably have to scale back the abilities to be in line with other familiars though.

Zombie squirrels are all the familiar a necromancer needs.

Step 1:
Animate Carrion
Level: nec 1 | Range: 10 feet | Duration: permanent
Raised are the bones or carrion of Small animals: amphibians, birds, mammals, and reptiles of natural
sort. The undead animals will obey the simple instructions of the caster (essentially one-word commands) and follow him unless either slain or turned (see Vol. III, p. 252: Combat Actions, magic); the dispel magic spell (q.v.) also will nullify the connexion betwixt the sorcerer and the undead animal. The caster can animate and maintain no more than 1 HD of undead animals per CA level. Whether or not desiccated flesh remains on their bones, the undead animals have statistics as noted in Vol. IV. Animated carrion loses
any special abilities possessed in life (e.g., flight, musk, venom).

Step 2:
Small Undead Animal
(Undead Type 0)
No. Encountered: 1 (1d6)
Alignment: Chaotic Evil
Size: S M
Movement: 30
Dexterity: 10
Armour Class: 8
Hit Dice: ½
Attack Rate: 1/1 (claw, bite, etc.)
Damage: 1d4
Saving Throw: 17
Morale: 12
Experience Points: 9
Treasure Class: —

Step 3:
"The zombie squirrel attacks!"
 

Ghul wrote:

Yes, the necromancer in my group had his own special sled dog familiar, much as Handy described with his squirrel example. The other dogs in the sled team just couldn't get along with him, though. And he was too slow. ;)

Nevermind it looks like it's permissible! 

Ghul wrote:

Yes, the necromancer in my group had his own special sled dog familiar, much as Handy described with his squirrel example. The other dogs in the sled team just couldn't get along with him, though. And he was too slow. ;)

I never could train my dog not to eat the skeleton dogs. It's like rule 0: dogs like bones.

You don't have to run faster than the undead dog. You just have to run faster than your friends.

Handy Haversack wrote:

You don't have to run faster than the undead dog. You just have to run faster than your friends.

True...perhaps I should have said "longer", not "faster". 
In any case, I fully support my players being imaginative with the rules, which I treat as a framework in most cases.

Hackhamster wrote:

Looking at playing an Norman Bates-style Necromancer (quiet, unassuming, polite, but crazy and homicidal) that just happens to carry his mother's head around with him in a pickle jar.  He talks to it. It answers him. Among other things, it tells him to leave the girls alone, they are only trouble.

Either that, or "What if Tom Bombadil was actually a grave robber?"  Then I could have my own undead Fatty Lumpkin.

 

Immediately reminded me of the style of Creepy or Eerie Magazine. Cool!

 

rhialto wrote:

Hackhamster wrote:

Looking at playing an Norman Bates-style Necromancer (quiet, unassuming, polite, but crazy and homicidal) that just happens to carry his mother's head around with him in a pickle jar.  He talks to it. It answers him. Among other things, it tells him to leave the girls alone, they are only trouble.

Either that, or "What if Tom Bombadil was actually a grave robber?"  Then I could have my own undead Fatty Lumpkin.
 

Again, I'd welcome this kind of creativity in my game: well done! 

Once Jerry the Body-snatcher is able to animate dead, he's gonna sew mom's head onto a convenient corpse and then it's on like Donkey Kong.
 

I would add brain in a jar to the list of possible familiars. Their creation is through Mi-Go technology beyond the reckoning of man but occasionally sorcerers discover and make use of them.