Inspired by a thread where Emmett Shear very patiently argues with someone about Newcomb's problem, here's two variations. I'm sure they've been done before but that's OK. I'll assume familiarity with the problem; if you haven't read about it, go do that first! It's a fun thought experiment.

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Relativistic Newcomb

You and Omega shake hands, synchronize watches, and get into spaceships traveling at the same speed at opposite directions. When you get to a light-hour apart, a timer goes off on each of your watches: at this point Omega makes its prediction and either does or does not put money in the opaque box, and you commit (and write down your commitment) to taking or not taking the opaque box. Then you both turn around. Once you meet in the middle, you get the contents of the box or boxes you've chosen.

From your perspective you're chosing before the money is actually placed in the boxes, but from Omega's perspective it's putting the money in the boxes before you make your choice. So Omega is truly making a prediction, but nevertheless at the time you make the decision you can't say that you're "already in" the world where the opaque box contains or doesn't contain money.

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Sleeping Beauty Newcomb

Instead of Omega you are confronted with Morpheus, god of dreams and prophecy. He is going to put you to sleep, then wake you up and offer you the two boxes. Whichever choice you make, he'll immediately put you back to sleep and steal your memory of the past few minutes. He'll then place the $1m in the opaque box if and only if you chose just the opaque box upon first being woken.

Then he wakes you up again, with no memory of the first awakening, and offer you the boxes again. From your perspective, there's no way to know whether this is the first time you've been awoken or the second. Which boxes do you take now?

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Unfortunately neither of these really adds much if you already 1-box. I'd love to get variations which probe similar edges of the experiment but for 1-boxers.