Polymorph Query

[AnimeTheCat]

I shall preface my questions with the following limitations:

You are a:
-Level 7 Wizard with the Polymorph spell, OR
-Level 8 Sorcerer with the Polymorph spell

You are limited by:
- Spell Slots, you have exactly 1 4th level spell per day, you don't get any additional spells per day regardless of any items, attributes, etc.
- Spells Known, You only know Polymorph, you may not ever learn any additional spells, no matter what.

Based on those two characters with that singular spell and other confinements, what monsters from the MMI would you polymorph in to and why? If possible please limit your responses to you top three monsters.

[Kaleph]

I shall preface my questions with the following limitations:

You are a:
-Level 7 Wizard with the Polymorph spell, OR
-Level 8 Sorcerer with the Polymorph spell

You are limited by:
- Spell Slots, you have exactly 1 4th level spell per day, you don't get any additional spells per day regardless of any items, attributes, etc.
- Spells Known, You only know Polymorph, you may not ever learn any additional spells, no matter what.

Based on those two characters with that singular spell and other confinements, what monsters from the MMI would you polymorph in to and why? If possible please limit your responses to you top three monsters.

Strange question - depends on the challenge, since I'll use polymorph only in 1 specific event per day - and obviously I'll pick up the best form to deal with that specific challenge. In any case, I'll try to make some example of shapes I'd consider my best picks in most of the occasions.

Typically at CL 7 I like the Annis, due to the large size, the extraordinary Special attacks and the good stats. Of course I'd cast it on the party tank (or glass cannon).
Again at CL 7, a Wyvern is large, flies, has improved grab, multiattack as bonus feat, has 4 natural attacks, it poisons and has +8 NA. It could be a nice option when you're in need of a flying form.
A Remorhaz is huge (!), has burrow Speed, improved grab and swallow whole (!), which is a nice set of abilities for a level 7 character.
Finally, the Treant is fantastic. It's huge (!) and it tramples, has +13 NA, deals double damage against objects, gives nice boosts to stats and skills, and your DM may easily rule that they're of general humanoid shape (and thus you keep your equipment). According to this article (http://archive.wizards.com/default.asp?x=dnd/rg/20040525a), you also get some of its immunities (natural abilities):

mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects)
poison, sleep effects, paralysis, polymorph, and stunning
critical hits


I know I gave you 4 monsters and not 3, but it's still a small number, which provides a nice array of abilities, and therefore I think you'll be ok with it.

EDIT
A CL 8 sorceror will most likely have even more options at his disposal, of course...

[AnimeTheCat]

Strange question

I know that the formatting of it was strange, but the idea was to ensure that it was isolated to only be a function of the Polymorph spell, not what I can have happen to me from a string of xyz spells that includes polymorph.