Not necessarily my favorite memory, but managing to beat the Bed of Chaos with my own creative method that I haven't seen anyone else use was pretty fun and satisfying. Like everyone else, I was having a hard time trying to avoid getting knocked into those death pits, but I figured out that I could just use the Iron Flesh pyromancy to make myself heavier. It does slow your movement, but as long as you just block all of its attacks with a Greatshield, it'll make it impossible for you to get knocked around.
Similarly, a lot of people don't seem to realize that bonewheels will not attack you if you use the Hidden Body sorcery, which I also figured out through experimentation.
Finding the Painted World on my own was also very satisfying, especially after having multiple people say that I'd never find it because of my stubborn refusal to play online.