Hmm .. it seems like most people are talking about what I like to call 'bro-sad' things, or 'Gladiator'-sad.
I found the death of that kid in Dragon Age to be the game writers throwing down a gauntlet. I can't say I actually cried, but it made me stop and wonder 'will the game designers *actually* go through with this?!'
I have to say I kept expecting some other character to walk in an say 'waaaaait! luckily, I know what to do!' and save the kid despite me screwing up. But nope ... I had to stand there, impotently, and watch an already emotional wreck of a woman slit her son's throat and hold him sobbing as the life gushed from him, until he became a small, cold, dead hunk of meat.
And, although it wasn't my fault, it was my failure to act accordingly that saw this happen.
Perhaps being a parent made it more poignant for me, rather than others here?