On Episode 149 of the Thinking Poker Podcast, Andrew and I discuss Rounders with Brian Koppelman, one of the movie's co-writers. One question that comes up is whether Teddy's hole cards, in the climactic hand, are briefly visible on screen. Andrew has asked me to post the screen shots to which I was referring.
On the show, Brian claims that the cards aren't visible. He's arguably right about that insofar as what appears on screen (or at least what appears below) doesn't provide conclusive evidence for any specific pair of cards.
They occur at roughly the 1:50:33 time stamp on Netflix. Here they are: