My top 10 SHTF movies are:
1 - The Road
2- Arctic (Extreme environment survival)
3- The Day
4- Contagion (although I don't like how they focus on vaccination as the answer to pandemic or the film's propagandistic treatment of vaccine skeptics, it's Hollywood and they always push the globalist/leftist agenda, so... At least the parts where looters were invading homes, robbing stores, mobs bumrushing pharmacies, police & other emergency services overwhelmed, people running out of food & other necessities and subsequently rioting, society breaking down all around, et cetera, provided some needed realism. Even if some of these things were inferred in the movie, there's enough depicted in short scenes to connect the dots. And with what's going on right now in China, now is a good time to get full-face respirator masks, purell, hard surface germicidal/virucidal wipes, nitrile gloves, and other pandemic preps.)
5- How It Ends
6- No Escape (SHTF/WROL when you're in a foreign country)
7- Into the Storm (Tornadoes)
8- I Am Legend / The Omega Man (both versions are good)
9- Deep Impact (Asteroid strike)
10- Children of Men (Global infertility)
Honorable Mentions
Doomsday
Outbreak
The Day After
The Postman
Assault on Precinct 13 (2005 remake) (WROL situation)
I'm sure there may be some other good SHTF movies out there, but I made a point of excluding anything of the sci-fi genre (like The Andromeda Strain 2008 remake) or zombie movies because that just wouldn't happen in real life. The only zombie movies that are even somewhat plausible are 28 Days Later & 28 Weeks Later, and that's really almost a pandemic movie than actual zombies. So maybe throw that in with Honorable Mentions.