Is it possible to make a large spike spear up out of the ground to attack a target? (Last Air Bender references)
If so what damage would it be?
Can Stone Shape be used to make bullrushes?
The spell's duration is instantaneous, so I'm thinking that it is possible but the spell is pretty vague on its uses.
No and no. But it can just trap them in a box of stone and other unfair nonsense like that. Stone Shape is crazy good.
The stuff you're talking about (Spikes from the ground and bullrushing) are really done by other spells. You could likely talk to your GM about refluffing a spell like Hydraulic Push to be earth-based.
There is no strength score affilated with Stone Shape, nor a saving throw. You can't lift anything off the ground with it, contest a strength score, or use it proactively...it has no strength.
Think of it like reducing the stone to a semi-liquid state as you shape it. It won't spread against any pressure, but you can mold what is there as you see fit if there is no resistance.
==Aelryinth