PlayStation Move controllers worldwide. Alas, that number has been widely misreported as the tally of direct end-user sales, which it most definitely is not. What Sony's letting us know is total wands that have left its warehouses on their way to retailers, a number that's one step removed from actual sales results. Still, if you simply must have something to compare against Microsoft's 2.5 million Kinect sales, there you have it.
Update: Our brothers at Joystiq have reached out to Sony and confirmed that these numbers represent shipped units, not consumer sales. Here's Joystiq's exact wording on the (seemingly purposefully) confusing situation:
A Sony representative explained that the 4.1 million actually represents Move units shipped to stores, adding "While we don't disclose our exact sell-through number, the key is that our retailers continue to ask for more Move units and are taking every unit we can supply them with based on their sales." Which, you know, would have been a cool thing to put in that press release, we think.
Update 2: We've also confirmed with Sony that the sales numbers are in reference to retailers, not consumers, and learned that more than 75 percent of the sales in the US are bundles -- meaning new console sales or software groupings.