Um, judge?

In general, you shouldn’t be shy about calling a judge at a tournament. It’s not automatically a commentary on your opponent — you can always just say, “I’m just not sure about this situation, so I’d like to ask.”
In round one of today’s PTQ, in the game immediately next to me, everything ground to a complete halt when the guy seated beside me played a Wrath of God.
Pause. Silence.
“That’s not legal in this tournament.”
“It’s not?”
“Um, judge?”
When the deck was checked, the guy had twelve Tenth Edition cards in his deck, including four Wraths, four Llanowar Elves, and some other kind of removal. He’d thought that Tenth Edition was also legal in block.
Faced with the option of replacing twelve cards in his deck with basic lands, he chose to drop from the tournament.
That’s certainly the most interesting judge call I’ve ever been near.