Red light, a y that has an explosion attack that causes paralysis. This is a reference to red lights in real life making you stop.

(There could also be green lights whose explosion gives a temporary speed boost, but since this isn’t harmful to the target it’s a sillier idea.)

Chatting to a pet that is carrying an item picked up off the floor will command them to drop the item. The odds of them obeying depend on their tameness and apport.

Teleporting no longer checks to see if there is a monster present on the destination tile. Teleporting into a monster’s space has a chance of telefragging and instakilling it. (Though for fairness this should also happen to the player if a monster randomly teleports onto their space.)

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.

Player status called Terrified: it acts like confusion and stunning in that it makes you move in uncontrolled ways, except that it pathfinds away from whatever is scaring you.

A magic trap that causes you to yearn for your distant homeland may instantly magic portal you to your quest home level (perhaps asking you first).