Having quite a few nail/screw/wire/pin punctures in the last few years, this surely wasn't what I expected to see

 hahaha! non of the above
I think what happened is: please look ▼

 no, I was not playing with a drill

 Then ti was bitch blood!

 I was asking the same myself for 10mins...

 how did this happen? it would take some force to push that bit of tube through the rim..?

 Happened during regular road ride. My theory is that this metal rod was touched with the front wheels and jumped off the road slightly. When the rear wheel approached millisecond later the rod must have been positioned perpendicular to it and went through all layers with ease. This wasn't a gentle thorn sting, it was like a screwdriver stab and immediately left me riding on completely flat tyre.

 yeah but through the tire, inner tube AND RIM? i would of thought flight would come before full penetration of rim...amazing.

 i would think if you called the rim company and explained this, they would give you a free replacement as it's so unusual, you might point out their rims are soft!! in the pics it looks like the 'rod' that penetrated the rim is made of aluminium, which is quite something, try pushing it through another part of the rim, i bet you cant!

 Thanks for the suggestion, I may do so.
PS. I'm not talking about trying to make another hole )

  i got it! let me know the response from them

 I could not resist recording it... and I even shared my surprise with random pedestrians

 Well, as Robby said, probably one in a million. A perfect alignment of even strongest materials can make a perfect cut
I put my theory replying under 'baggyferret'

 Wow! How do u propose to plug the hole in the rim?

 I left it open. It's hard to spot it and doesn't really bother me, plus having a 33-spoke rim seems pretty cool