As seen here, you can find a manifest of nearly every Item ID currently in the game. This includes items that are fully implemented and ones that are not.
I decided to look through this and find items that have IDs but are not yet accessible. There’s dozens, with some having reasons to remain unused while others may have just been forgotten with time. I’ve compiled a list of the ones I could find and organised them into categories that they fall into.
I’ve specifically ignored Upgrades, Arcade, and unused Milestones to condense the list, I’ve also exempted the Workshop Items since that’s a major update on its own.
Accelerate Game World Items
These are items that were originally made for Accelerate maps. While Accelerate is not yet finished, many of these items visually seem finished.
Many of these originate from Sunrise Isles and fit a tropical theme (which especially meshes with the setting of Villa) while some come from Pine Valley (2103 - 2113). Preferrably if these items are not finished, the Camper should have an opening door and interior. Also new Lighthouse PLEASE.
These are items that were temporarily given an ID and Visuals, but lack any function. What’s odd is that there’s many items in the game that can be currently be purchased that are like this (the Blender, Present, I/O). These don’t specifically need to be added now, but I’m including them for posterity.
While two Disco Ball items come from the Arcade, these are entirely separate and seem to be music visualisers.
173 - Disco Ball
174 - Rave Ball
While the two Button types that have existed since extremely early on are purchasable, there are two other I/O items that exist in the IDs that have yet to be added to the Catalogue.
556 - Keypad
2146 - Target (presumably)
Toys / Interactive
The infamous guitars are located here, but there also exists another item that I recently requested.
176 - Guitar
179 - Retro Guitar
2139 - Viewfinder (Plaza Binoculars)
Furniture / Building
These are assorted furniture items that haven’t made the cut yet. I’m a big builder and I love having options… and some of these are simply options that I’ve been missing trying to work around.
386 - Spiral Stairs [Presumably this is a scalable set of stairs similar to the existing stairs item]
733 - Casino Railing
843 - Glass Banister
844 - Brick Fence
846 - Victorian Fence Short
847 - Victorian Fence Post [we already have the fence counterpart]
2140 - Indoor Casino Door [Notably there is only an ID for a single door, double variant would be appreciated. I also have a megathread of every unusable door that the devs no doubt despise]
2141 - Indoor Casino Window
707 - Antique Wall Light [Likely the ones found in Highrise]
708 - Ceiling Light [“A wide fluorescent hanging light, great for illuminating hallways”]
710 - Dual Lights [Would have two controllable light sources, probably didn’t work with current limitations]
712 - Cylindrical Ceiling Light [Different from Spacelight, seems to work with 713 to create continuous light fixtures]
713 - Curved Ceiling Light
824 - Iron Chair [Reference to the Iron Throne? Maybe a replacement of the HL2 Blue Metal Chair?]
2137 - Ticket Machine [Seen in the Arcade]
2142 - Chalkboard [Possibly interactive, displaying text]
2144 - Check-in Kiosk [Possibly the Condo Desk in the Plaza. Or perhaps related to the Condo feedback system]
2145 - Washing Machine
730 - Beach Umbrella 1
731 - Beach Umbrealla 2 [In the Plaza already, they exist to mock us. I requested this previously for the 2021 Summer Update]
2003 - Tombstone [Included with the Halloween 2020 event items]
2132 - Delivery Truck [Seen in ZM Gasoline]
2133 - Motel Sign [Seen in ZM Gasoline]
2134 - Star Fountain [Seen in Virus Deserted]
2136 - Round Fountain
2136 - Market Stall [Either from Virus Deserted or LC Market]
2143 - Outhouse [please]
There’s also of building blocks that were meant to compliment the PBB furniture set and allow you build around them.
Outside of Milestones and the Arcade, there are surprisingly still a few unused Equippables.
470 - Umbrella [Maybe it’d slow your fall-speed?]
2005 - Spooky Wowozela [Added in Halloween 2020, presumably related to the Halloween Catasack]
2138 - Golf Cart [Vehicle Variant of the RC Milestone]
I feel the Furniture / Building section is the segment that should be finished first since many of its items do not need unique programming. And many items in that category are niches that are noticeably empty or barebone (Fence and Door variety namely).