Here's what I know. I'm pretty sure each list is complete, except the hat bag. I know I'm missing a bunch (edit - Added a bunch more).

10 bag (gralats):

- 10 to 40 gralats (don't know the exact range)

100 bag (furniture):

- Pumpkin pet
- Ghost pet (cartoony version)
- Spider pet
- Cat pet
- Apple Bobbing Coffin
- Coffin Bed

200 bag (Usable items):

- Flaming dog poop bag bomb
- Pumpkin pogo
- Bone Juggle

325 bag (Hats)

- Silver Trimmed Tophat
- Gold Trimmed Tophat
- Black Tophat
- Diver's Helmet
- Ghost hat (covers head)
- Tarantualla hat
- Blue warrior-type helmet
- Chattering Teeth
- A tree hat
- A clown beanie
- Viking Helmet
- Skull Mask
- Various Recoloured Tophats with a feather

1000 bag (Mount):

- Chimera