A sheet of Mob. As I was gripping my new deck (which has a steeper overall concave), I set the sheet of grip onto the board, and when I was patting it down, the grip cracked, right at dip of the board (at least I think it's called the dip, it's the area of the nose or tail right above the bolts where it is just starting to bend, not sure what the official name for it is, so I just call it the dips). The shape was too steep for the grip so it crinkled/cracked when I put it down.
Now I know it's more just cosmetic damage rather than anything serious, but I seriously could not look down at my board only to see a giant crack looking back at me, it was too distracting. So I went back to the shop the same exact day and bought a sheet of Jessup.