Density Control

[Gazirra]

How about Weight Manipulation? Basically, Density is mass over volume (g/cm^3, for example) Increase weight, but keep volume constant, and you can manipulate density
Or maybe Shrink You can reduce size but not mass, or both mass and size, thus altering density also. Growth probably wouldn't alter density too much, due to the mass increases with the volume increase.
Or how about the power I just remembered: Control Density. Seems a wee bit obvious now that I look at it.

[The Baron of chaos]

Intangibility had often being presented in comics as a form of personal density control. the opposite of scale would be APS Stone, except the character woudl still look normal, only as dense as a diamond. Weight Manipulation had already be pointed out, as well as the most common used minor powers.

[Yukon]

i made a character that can increase his density. i just gave him growth and took away the size increase.