2024/01/26 Update: Find All Items is working! Have at it.

So you've decided to try to find all the items in this game. My condolences.

I initially created this checklist purely to help myself in my hunt for items in the game, but it sort of ballooned into a bigger project so I decided to make the list available as a guide.

I dug through the game files for the information contained in this guide, but the files are not very organized and fairly hard to parse (especially when you're doing 400 of them), so there are a few items for which I don't have complete information.

(this information may no longer be true) For the purposes of the Find All Items achievement, only the base game items count. This is not reflected in the description on the Steam side of things, but is indicated in the in-game achievement list. This is also true of the Safari and Unlock All Items achievements. The DLC items (or most of them, anyway) are tagged with "Au" in the spreadsheet.

Final notes:

• Any empty fields in the weighting column can be assumed to be 100 (default) weighting.
  
• Some of the item pool sections are incomplete; the items may appear in more pools than are shown.
  
• Many items have a listed credit cost even if they are not in a shop pool; this is future-proofing on the part of the devs and can be disregarded, but I included it anyway.
  
• DLC (Au) items only spawn on Gold floors, which have a slight visual difference to regular floors and different enemies/minibosses/bosses with the (Au) tag. If you're hunting for a non-DLC item (which is likely), you should be looking on non-Gold floors. Exception: DLC robots (familiars) can drop on both Gold and non-Gold floors.
  
• Take floor information/spawn pools with a grain of salt - I have found some items outside the posted spawn range or in the wrong pool (including, notably, Decimating Power in a level 1 item room).
  
• Level-Up Perks are technically items (I think), so I've included the list at the bottom.

Here is the link to the spreadsheet itself.[docs.google.com]

As with most spreadsheet-style guides, editing is locked on this copy, but you can "Make a Copy" (under the File menu) in Google Drive to have your own editable version.

There is a Legend included on the right-hand side at the top, which will help you parse the abbreviations I used.

You might notice the full item list is still quite a bit shorter than the in-game counter. This is because both Incredibilities and Level-Up Perks are included in that counter. I don't currently know if base game Level-Up Perks are part of the requirements for the All Items achievement, but I'll find out soon. Also, I believe the current Level-Up Perks list has some unobtainable entries, which may be fixed in a future update.

Extra special thanks to Logorouge for telling me about the information in the game files, and for telling me a lot about the nitty-gritty of item generation and other game mechanics.

Hope this is helpful to somebody. If you have any questions or comments, let me know.