My child has been swinging in our front yard (NC, US) and worn away the grass, revealing this metallic stake (* See photo, note the acorn top for scale*):
I gently tried to pull it up, but it is lodged in pretty well, and I don't want to damage city property it could indicate a gas line or something important. I don't think it is a ground rod (it seems to be stainless steel).
As it is right under her swing I'd like to remove it as it is a safety hazard, but I think I probably shouldn't.