Looking back, there are only 4 moments in 3 videogames that were just too much for me to keep a straight face on.
Final Fantasy VII
Lost Odyssey
Mass Effect 3
Final Fantasy VII
When Aerith died, and when Cait Sith died
Lost Odyssey
When Kaim watches Lirum fall off a cliff and presumably die
Mass Effect 3
If you mess up the quarian/geth thing and watch Tali commit suicide