Ways to gain Improved Grab without size limits?

[123456789blaaa]

(Not sure if this should go here...it's a pretty simple question anyways)

Exactly what it says on the tin. The only way I know of currently is were-octopus.

[Maat Mons]

Well, were giant octopus, were squid, and were giant squid also work. 

The scorpion's grasp feat (Sandstorm) has the effect you're looking for.  It's not explicitly improved grab, if you need it for a prerequisite. 

You still have to make the initial grapple check, and it still automatically fails if the creature is two or more size categories larger than you.  The only thing I know of that gets around that is mimic. 

[zook1shoe]

Feral
Were-other animals with imp grab
the bug lycanthropy on a vermin with imp grab
Tauric imp grab creature
symbiotic imp grab creature

those are the ones I can think of at this moment

[123456789blaaa]

Do those methods explicitly say that they bypass size limits? I'm asking because of this sentence in the SRD:

Unless otherwise noted, improved grab works only against opponents at least one size category smaller than the creature.

[zook1shoe]

Some creatures do, which many of those could be Symbiotic/were/Tauric material

[Ithamar]

The Anthro-Octopus & Anthro-Squid should also have that ability, and are low enough ECL that they might almost possibly be potentially playable in some manner.

[zook1shoe]

Dung and whipsnakes in Serpent Kingdoms have no limit on size for imp grab, both have 3HD

[Maat Mons]

Dung and whipsnakes in Serpent Kingdoms have no limit on size for imp grab, both have 3HD

The entries for those creatures don't mention size limits for improved grab at all.  That means they inherit the default size limit, up to one size category smaller than themselves. 

[zook1shoe]

But it gives all the text of the ability, you can assume that when it says 'when it hits with its bite, it can grapple any creature (with the normal restrictions over grappling something too large)

more evidence this is true? The deathcoils in the same book actually lists the max size as is in the 'standard' ability.

since these are in the same book, you can assume they intended for 'no size' for these snakes and many of the other monsters in Serpent Kingdoms