A spool of wire that would leave wire wherever the holder walked, like in the level editor. This would affect the logic of the level in real-time. Wire still wouldn't be place-able on colored floors, recessed floor panels, etc.
Cursed medallion that, when picked up, would prevent the holder from dropping any items. Could only be taken away by a red thief.
Some kind of block that doesn't activate pop-up walls or sink turtles.
Green CC2+ chips/bombs that don't add to the total chip count.
Wire that's deadly while it's active. It would be red while inactive, and yellow while active, so it could be easily distinguished from normal wire.
Bowling ball-esque item that doesn't have an inventory, but moves at a speed boots pace, and if it hits something that can normally be destroyed by a bowling ball, it instead causes the thrower and the target to swap places. If it's fired from a clone machine, it causes the target to switch places with whatever is currently inside of said clone machine.
Trapdoor that turns to normal floor once any moving object falls into it.
Some item (blessed medallion?) that, if its holder is Chip or Melinda, does not cause the player to lose if the holder dies and there's still another Chip or Melinda to switch control to.
Gauntlets. When the holder has these on, they can push against an enemy to change its direction. This would also give Chip and Melinda immunity to enemies while pushing against them.
Forklift or something. When the holder has this, they can push directional blocks in directions they're not meant to go, and can push any combination of multiple types of blocks (including dirt blocks). When used with a hook, this can pull directional blocks in directions they're not meant to go.