I only saw it once and I was a teenager so maybe my view would be different now but I hated It's a Wonderful Life! It's one of those films that's supposed to have an uplifting message but just leaves me feeling utterly depressed! I don't say I don't think it's good, I only say that it made me feel really depressed so is certainly not a film that I'd put on the tear jerker list. Thus it's not a universal tearjerker...
Hard to remember things that moved me the most, but I just saw this for the first time and cried A LOT! It is so sad! And not just at the end - at many points. John Hurt is utterly heartbreaking.
However the saddest film I've ever seen is definitely Truly, Madly, Deeply 'Course I'd put this in the list too, thus…. The Elephant Man and also Cinema Paradiso. I have to be honest - I've done sobbing at a fair few films though that I can recall so maybe I'm not the person to ask.
I cannot agree more with your view on It's A Wonderful Life .... barring the final 10 minutes of that movie, it is just a soul-crushing experience ...
About the original thread topic though, my addition to the list would be Jim Carrey's "Truman Show" where he first showcased his acting talent (in my opinion) and showed that he is more then just a rubber faced comedic genius. I found it difficult to hold back when he tries to swim away in the ultimate act of desperation and finds out that even then he LITERALLY ends up hitting a glass wall ... powerful stuff