Iron golems rust in multiple stages, like iron items, rather than all at once. Each stage cuts its maximum HP by 20 (so a rusty golem has 60 max HP, etc.) Applying a can of grease will remove the rust and restore its max HP to normal, and may prevent further water damage for a little while. The golem may also quaff a potion of oil, which has a similar effect, except it also restores current HP as well as maximum by the amount of erosion removed.

Iron golems that rust to death may rarely leave behind a statue (ideally made of iron material) which is implied to be its rusted husk.

Greasy floor, a new type of terrain (or perhaps a trap?) that applies grease to any boots you are wearing and almost always makes you slip. Slipping on greasy floor (which can also happen by walking barefoot or with already-greased boots on) causes you to drop random items, some of which may get greased.

The player can create greasy floor by smashing a potion of oil or applying (multiple?) charges from a can of grease to the floor.

Creatures that move onto a greasy floor patch may “slip and slide and struggle to stay upright”, losing their next turn 70% of the time. This also happens to a creature standing on a greasy floor patch that tries to do something involving footwork (combat, moving off the square, etc) 30% of the time. Or for a more simplified implementation, the trap doesn’t have to cause loss of turn when moved onto (though it might still produce a message), but has a 70% chance of making the creature lose its next turn regardless of the action (still need to keep your balance to take out a scroll to read or zap a wand, for instance).

If implemented as a trap, it cannot be untrapped (except probably by the standard method of digging a pit on it), but will eventually wear out after a slightly randomized number of times it affects something. (This prevents you from setting a single one in Ludios and then standing back to watch the whole army get greased and fall over themselves.)

Artifact can of grease, the power of which is to grease your entire open inventory when applied (consuming a charge like normal), in zero turns. Or for a slightly less greasy effect, allow the player to pick any subset of their inventory they want to grease in one go.

You can apply a can of grease or potion of oil to a door to guarantee that it will close and open without resisting.

A tinning kit’s weight is dependent on how many charges it has left, getting lighter as it is used to tin things. This could also be extended to other tools which have charges and are not magical, such as cans of grease.

You can read the label on a can of grease. This reads “Yendorian Grease. Caution: water-soluble.”