Hmm.. Off the top of my head, the game that I think of is Red Dead Redemption. It had some really nasty random encounters or situations that were huge spikes in difficulty almost to the point that you were meant to die from it.
The woman asking for help while standing near a broken wagon. Once you got pretty close to it, several bandits would spawn in a big cluster within a few feet of ya. I would rarely use the dead eye/freeze time ability. I died I don't know how many times in a fraction of a second from this random encounter because they were clustered up and so close to me.
The other situation that was more common but more frustrating cause of death for me are the mountain lions in that game. One would be chasing me and I wouldn't be aware of it. I slow down or stop at some point, the cat runs up and kills the horse so swiftly before I could react. I fall to the ground and the cat runs up to me, paws me to death before I could get up. The noises they made were very easy to miss.
Those were the most frustrating deaths in a game to me.
