Pong, What an epic struggle between the two paddles, friends at first, now forced to kill each other in an epic pingpong match,
and Ninja Gaiden, out of frustration.
This. This more than any other. It didn't help that I had just replayed HL2 and Episode One to refresh myself prior to playing it. I had become so invested in the characters. Heck, I nearly cried prior to that in Ep2 when I thought Dog had died when he was fighting that strider. But the ending was just...man. For a couple days after that, just thinking about it nearly made me cry. I rewatched the ending the next day, which was even worse. But I just kind of had to see it again. If only there were an Oscar category for best voice acting in a game. Merle Dandridge should've won one.
There's been other games though. There was at least one time in each of the Gabriel Knight games.