Dental floss. But of course, that has to be it. How stupid of me not to see it earlier. And it neatly explains those US army doctors scrutinising Saddam Hussein's teeth when they captured him all those months ago. Obviously, as I now realise, they were looking to see if he had any plaque and checking for evidence of waxed minty dental floss, alias WMD.
For dental floss, clearly, is a controlled substance. I mean, how else to account for the fact that it is sold here only in small dispensers and teeny weeny lengths. It's not as if dental floss has a best-before date, or decays into dust after 30 days. There has to be some good reason to justify all the extra packaging. So it must be because this is dangerous stuff - weapons-grade thread (as anyone who has ever inadvertently caught it between their molars will agree) that must be regulated.
And of course, as with all lethal objects, floss is widely available in the US. Sold in large tubs by the mile, to folk of all ages. Why, even kids can buy it without a licence. Here, you are lucky if you can get your hands on 50 metres of the stuff. There, you can buy it in bulk in 250-metre lengths, minimum. Enough for an army, you might say.
And that is why, any time the other half heads for North America, he is given strict instructions to return with a case full of Saddam-size tubs of floss. Happily, one consignment will satisfy our habit for years. Which is just as well, because on these trips the other half is inevitably scanned and swabbed by airport security - something we used to attribute to the beard and to the physics book he invariably carries on board (and yes, I know, quantum field theory does indeed look like rocket science to the uninitiated); but I now realise these inspections are due to his WMD trafficking.
My big worry is that floss will soon be banned by airport security, if it isn't already. And then where will we be? Scrounging it by the metre? Recycling it (best not to dwell on that option)? Resorting to machine cotton? Launching a WMD campaign, with supplies flown in courtesy of the military stop-over at Shannon? Or reduced to wishing for an ideal world with economy-sized drums of waxed or unwaxed, minty or plain.
Ah, that ideal world. It would have, while I'm wishing, not just all the dental floss you could want, but also Dublin Bus 10-journey tickets that would indeed be 10-journey tickets, and not 10-journey tickets that must be used within six months (so-called handy packs). Cue: sound of hysterical laughter. I mean, what's handy about that? The whole point, surely, of a 10-pack of tickets, is that you keep them handy in your wallet until you find you need one, Not until you find you need one but it's out of date.
And another thing. You'd be able to exit from my Utopian Dublin buses by the back door. How novel (and time-saving) an idea is that? And - why stop now, when I've so much to get off my chest? - in this Utopia of mine, till receipts from shops would print only part of my credit card number, with at least four of the digits replaced by asterisks.
That way, there would be no security risk when I bin the receipt. Call me naïve, but I'd have expected the banks would insist that all merchants do this. But no. Penneys in O'Connell Street, Dublin, to pick one receipt at random from my purse, is among the many that still print the number in full for all to see (Roches Stores, I'm pleased to report, has mended its ways in recent times.) And shop assistants would count out your change to you, instead of just giving you a fistful of money. And table staff in restaurants would not brush the crumbs into your lap when they wipe down the table. And all the chairs in the restaurants would wear rubber socks on their legs, eliminating that awful scraping sound every time someone stands up, sits down or moves a chair.
And library users would turn off their mobile phones (yes, that's you I'm glaring at - you, sitting under the sign that politely asks users to turn off their phones). And there would be a quiet carriage on every Iarnród Éireann train, with no noisy kids, no noisy phones, no noise at all.
And we cyclists would be appreciated and applauded for not taking our cars into the city, and not be run into the gutter as happens daily. And spare parts would be readily available and cheap, and we wouldn't be forced to buy a new gizmo for want of a widget.
And these minor things would be all we would have to worry about. And we would have safe, effective cures for AIDS, and malaria. And a real concern about the environment and the threat of climate change. And peace in Sudan and Palestine, and all those forgotten war-torn regions that were suddenly yesterday's news. And an end to poverty and homelessness. And New Year cheer would last all year.
Well, no harm in wishing.