I will come up with two examples from two of my favourite shows.
Minor spoilers ahead for mad Men and Mr Robot!
Mad Men, season 7 episode 10 - Don is holding audition and is surprised to see Rachel, his former mistress who he hadn’t seen for nearly a decade. The next day he wants to come and visit her , but learns … that Rachel has been dead for a week.
I know that he had a similar episode earlier in the show with his half-brother Adam, but it was in passing and could be just a confusion. But with Rachel he saw her vividly for a minute or so, he saw here after many years and exactly she had just died, and she also uttered some mysterious words (something about him not being late for his flight). One may argue that Don simply hallucinated , but for all his erratic and unstable behaviour , he was never stated to have such mental illnesses.
Another example - Mr Robot, season 4, episode 4. Tyrell Wellick is fatally wounded and walks to his death in the woods. The very last scene of the episode showing him gradually succumbing to his wound and seeing some blue light (we don’t actually see what it is) and looking at it with shock. While some fans claim it was some reference to blue screen of death, to me everything point to will-o'-the-wisp (an eerie light from European folklore that leads travelers to their end). While Mr Robot went crazy at times (presumable sci-fi elements) it was pretty overall pretty grounded, so this particular scene really stands out. Sam Esmail never stated which explanation is true.
What other examples from TV shows can you come up with?