My 12" PowerBook G4 developed a little warp or bend so that it didn't sit flat any more. It would wobble on a desk as I typed - annoying! It all happened when I dropped it on the front corner, distorting the case.
A straight edge on the front palm rest clearly showed the bend.
To fix it, I removed the battery and put some slight pressure on the corner, reforming it into its original shape. Then I used a couple small vice grips, covered in cloth, to reform the case, trying to work out the dent "in reverse order in which it was created".
This process is much like how a body shop repairs a dented fender.
The repair looks great - it isn't 100% perfect, but close to it. Now it looks great AND it sits nice and flat on my desktop. And I didn't need to buy a whole new case.