The Will-O'-Wisp, best known for being absolutely ridiculous when combined with any template anywhere. Gravetouched Ghoul is most notorious, but many others work as well. Also they have the air subtype, which I'm not sure even does anything.

Sadly, the nine aberration HD pretty much ruin this monster. 50 ft. perfect speed and immunity to magic are nice, as is the natural invisibility, but with nine levels lost on an honestly sub-par chassis and no real offensive abilities (unless dealing 2d8 damage per round counts), I can't see wisps contributing much.

-0 LA.