Only LSD has taken me to what I would personally consider ego death - where I was capable of advanced symbolic thought (i.e., able to follow a more or less normal train of thought through to its conclusion rather than being totally overwhelmed) but temporarily lost the notion of an "I" that was active. I can remember the events in retrospect and they don't seem that... Weird, just me walking down a path thinking about ontology - but in the moment, it felt like my whole basic sense of self and other, internal and external, etc. had broken down, not in the sense of a visual OOB experience of anything, just conceptually. I found myself sort of rebuilding from scratch: "Okay, so I'm an I, a distinct subject... and I interact in this external world full of others... "I" is defined by that internal/external divide..." It took me probably a good half hour in this state before I was once again able to interact with the world more or less normally. Toward the end of the event as it was actually happening, the thought struck me that perhaps those who "don't come back the same" from a really intense trip go through something similar but... Screw up while rebuilding? Miss some fundamental piece of their ontology?
It was at once unsettling and immensely valuable as an experience, and while I have had many difficult-to-describe and intense trip peak experiences, none since has been quite like that one. That was on 8 tabs of supposedly 100mcg apiece (probably at least a little less, you know how it goes with tabs these days), so I was probably approaching saturation doses. High dose LSD is an insane but marvelous experience.
The most ego challenging experiences I've had with mushrooms include a trip characterised by physical misery and nausea where I briefly worried I might *actually* be dying and another much more positive peak experience that involved a long period of visuals I could not distinguish between open and closed eye... I can't remember what it looked like visually exactly, not much more than an amorphous blob from what I recall, but I spent probably close to an hour talking (well, mostly being talked to by) my own unconscious. This was very early in my readings of psychoanalysis and was one of the things that convinced me solidly of the theory that psychedelics achieve most of their meaningful content and 'weirdness' by exposing unconscious thoughts to conscious awareness - much like the theory about body sensations that basically says psychedelics cause the brain to read some internal nerve signal as external input, perhaps the same mechanical process is causing various pre-conscious elements of cognition to float to conscious attention when, for example, a peak experience seems to speak to your life events, traumas, current personal crises, etc. directly.