Good Polymorph forms?

[Lolzords]

Howdy, I'm starting a level 5 campaign soon as a level 1 rogue pixie. (sounds silly, but try it) One of my spell-like abilities is polymorph at caster level 8 once per day. I've already got remorhaz down, which is 7HD and allows me to do 2d8+8d6+12 damage per round if I swallow my enemy whole.

So, what other good up to 8HD creatures are there to polymorph into?

[Animefunkmaster]

Spell-Like Abilities

1/day—lesser confusion (DC 14), dancing lights, detect chaos, detect good, detect evil, detect law, detect thoughts (DC 15), dispel magic, entangle (DC 14), permanent image (DC 19; visual and auditory elements only). Caster level 8th. The save DCs are Charisma-based.

One pixie in ten can use irresistible dance (caster level 8th) once per day.

I don't see polymorph on there. If you traded any of the above in a special dm houserule, cool. Otherwise look at the spell in question.

The assumed form can’t have more Hit Dice than your caster level (or the subject’s HD, whichever is lower)

Also, I have always had an issue with polymorph and size categories since it functions like alter self which is specifically 1 size category difference. If this isn't a problem, Hydras are usually your best bet.

[Eldariel]

*shrug* 8-headed Hydra is pretty good. But eh, funkmaster has it right.

[Salt_Crow]

I believe Pixie's polymorph spell-like ability was errata'd a long time ago unless your DM has ruled otherwise.