A funny one for me, but it would have to be the first encounter with a regenrator in RE4. As a guy who was used to be hilariously irrationally afraid of zombies when i was younger, RE4 happened to be the first horror game I really got a decent ways in and was on track to beat. That sequence however, had me so shook up that I ended up turning the game off and deleting my RE4 save data off my PS2 right after (its okay I ended up going back to it months later and conquering my fear).