Which single product would you sell online if you could sell only one?

Here's a philosophical business question for the HN community:

Let's suppose that you had to choose one single physical product, just one, from every physical product known to man.

And let's suppose that you were going to sell it online, on your own website.

So the "rules of the game" for this thought exercise are as follows:

1) You're not selling Software, SAAS or a service.

2) You're selling a physical, packaged product that will be shipped to a customer that orders it.

3) You may not use Amazon's website in any way (i.e., via its partner programs) to advertise or take orders for your product.

4) You're using your own website, that is, you're not using traffic from someone else's website (Squarespace, etc.)

Now, which product (it can only be one single physical product) do you pick to sell and why?

A simple answer might be something like "You find the product which Amazon sells the most of, Amazon's current #1 bestseller... and you sell that".

But that's not a well thought out answer (I care more about the thinking process than the actual answer), because then my challenge question would be this: "OK, but you do realize that Amazon probably gets a deep volume discount from the product that is their #1 bestseller... how do you propose to do that if you don't have any volume?"

What I'm looking for is thought.

Tell me the one physical product you would sell, and WHY.

Let's have an interesting discussion!

Also, I'm not doing this to make anyone look wrong or stupid... what I am interested in are ideas, lots of ideas!