Title says it all . I play on the PC if it makes a difference, and can download mods.

Poisoned apples are unfortunately very tricky to use effectively. I've only gotten it to work once and it was more trouble than it was worth. In order for an NPC to eat a poisoned apple, that apple has to be the ONLY available food source in the entire cell. That means you must search every container and check plates/bowls/etc for any foods and withdraw them into your inventory. After that, place the poisoned apple in one of the containers that typically contains food, wait for the NPC's schedule to tell them they need to eat, and as long as there are no other options, the NPC should take out the poisoned apple, sit down, eat it, and then die a few seconds later.

EDIT: Oh yeah, as stated below, you can also just reverse-pickpocket it into their inventories. That works too, but I'm pretty sure it doesn't speed anything up. And from a roleplaying perspective, suddenly finding an apple in their inventory should make that NPC pretty suspicious!

First you need to remove every last bit of food from the cell you are in to prevent him from being able to eat anything else. Just taking it will suffice.

Next, you reverse-pickpocket the poison apple into the inventory of your unlucky victim.

Then, wait until he goes to eat. Since you got rid of all the other food items available, he will eat the apple you gave him.

:dead:

You steal his money. :biggrin:

I think putting it in their inventory alone does the trick. Im not 100% sure, but I don't recall ever having to empty the cell of all its nutrition..

It depends on the NPC's AI. If they're set to search for food within the cell, I think they'll eat anything else in there before eating the apple from their inventory. If they're already supposed to have food and they're set to eat whatever they're carrying, they go straight to the apple if you've removed the other food from their person. I could be totally wrong, but that makes the most sense to me and sounds pretty correct, based on my experiences with poisoned apples. :shrug:

It's a bit slow, but if you know the target's timetable you should be able to plan your attack to coincide with the time they're supposed to eat something.

EDIT // I'm a UESP addict, so I had to check because this started bothering me. It seems I was on the right track, NPCs that have no food in their inventory to start out with will eat anything else they can find in the cell before eating the apple. NPCs with food in their inventory will eat that first. The article was unclear on if replacing the food in the inventory with an apple would make them eat the apple, but it'd make sense.

EDIT #2 // It's also possible to create a potion from the apple, if you have any other alchemy ingredient with a scripted effect. If you name this potion with a long string of A's, the NPC whose inventory you place the potion in should drink it if they ever need a potion. You can't make a poison out of it, unfortunately, so it has to be reverse-pickpocketed.

I did this in the Imperial City and therefore two Argonians less :ninja:
I was actually about to strike one of them down normally, but before I got the chance he sat down and ate the apple :tongue:

What? Is this a mod? I cannot on 360.

No mod, but in vanilla there′s only one item which you can combine with Poisoned Apple and that is Rat Poison.
You can read more about it http://www.uesp.net/wiki/Oblivion:Useful_Potions#Special_Effects

Not a mod, like mirocu said. You can, you just need another ingredient with a scripted effect.

The complete list of all such ingredients can be found on the page linked by mirocu.

I read it.... seems like a lot of work just for that one effect.... and would break roleplay for me to do that Borderwatch quest, just to try it. Thanks. I'll just stick to removing food when I'm doing an assassination, and placing the apple in reach. This works every time, at least for me.

All you have to do is pick everything up in cupboards, shelves, barrows, boxes, themselves and what ever what is on tables in the whole joint. Pick their chests and pick up every food stuff and drinks. When you clear out everything put the apples on the table.
After that leave the place for a game week and sell their stuff.