Theres been some crazy ass weed highs that made me feel "alive". I still got a long journey to realization though.
So far I would have to say my first acid trip was the most profound thing I've experienced. It simply made me realize that we're all one and how money is pretty much the root of all our problems. I think The Beatles said it nicely. "I am he as you are he as you are me and we are all together." -I am the Walrus.
I'd have to say almost loosing my friends... And finding out they were all alright... Reality check. Nothin has come close to that yet. Had some amazing shroom trips tho... I want some booomers