Here is the full list of all 16 Graveyard Shift achievements.
Complete game in hard mode
Collect 1000 mushrooms
Score a 10000
Score a 1000
Score a 100
Complete game in normal mode
Kill 500 ghosts
Collect 500 mushrooms
Throw 500 mushrooms
Complete game in easy mode
Throw 100 mushrooms
Kill 250 ghosts
Collect 250 mushrooms
Kill 100 ghosts
Kill three ghosts with one mushroom