Certainly. I’ve tumbled upon many unexpected movies (and TV shows) on the TV that I didn’t expect to find.
Manhunter – Michael Mann’s original adaptation of Red Dragon blew me away. Unfortunately, I had to leave before it finished, but I hunted down a copy to see the rest.
Dr. Strangelove – i came across on late night TV. I’d heard of it, but nothing prepared me for how gripping it was.
Tales of the Darkside – they weren’t all winners, but the first time I stumbled across this show on a black and white TV, I had to check that I wasn’t watching an old Twilight Zone episode I hadn’t seen, or had forgotten about. It was The Odds, with Danny Aiello and Tom Noonan (who played the Tooth Fairy in Manhunter!), and it was very well written and performed.
The Terminator – from the TV ads, I thought it’d be some cheap SF flick with people in rubber masks running around LA shooting each other up. I was not at all prepared for the absolutely wonderful piece it was. Much as I like a lot of Mr. Cameron’s stuff, he never hit it out of the park like this one again.