Spec., Here's a few ( not in any particular order)
1. Not responsible for mismarked utilities or damage occured to such.
2. Extra charge for excessive rock ( boulders )
3. Extra charge for encountered ledge
4. Extra charge for excessive ground water ( pumping )
5. Extra charge to remediate improper soil conditions ( stabilization fabric / stone)
Seems like I just know the ones you charge extra for, I use them frequently
6. Another good one is all unforseen conditions just in case the one's above miss something