Sorry not a movie but a series: Chernobyl. Absolutely engrossing and gave me the chills from start to finish. 

yeah it's well done and it gives you extra chills because it's based on true events

T2.  No contest for me.  That's still my favourite ever movie-going experience.

Not my fave, but I quite like T3. The crane, the cemetery...

A Critical Drinker review reminded me of Clint Eastwood's "Unforgiven". That really was a magnificent Western.