Some good combos I've tried (and links to reports if they exist):
2C-I + 2C-C - Unique effect that was unlike either of them alone. It seemed to produce a very emotionally neutral state with the introspection of 2C-I and the smoothness of 2C-C, with unique, green/blue visuals and a tendency to make the written word look 3-dimensional (weird but described in
my report).
AMT + 4-AcO-DMT - Covered in many places. Extremely euphoric, ridiculous body buzz, strongly visual.
AMT + 4-HO-DMT - Similar to the above combo but less "buzzing" and more ego-crushing. I had a
very powerful experience on this combo a little while back.
2C-E + 4-HO-MiPT - This produced an effect stronger than either on their own and longer-lasting as well. Just total alteration. Recommended!
LSD + 2C-B - Produced a beautiful and glowing state that was different from either alone, and very deep. I spent 80 minutes of it laying down in bed with my eyes closed listening to music, and the CEVs were astounding. They were bright and vivid but very finely-detailed and fractallized like LSD, except not like LSD visuals in character. The trip centered on the concept of infinity. I also felt my consciousness split me from the top of my head out the bottom of my feet into equivalent vertical slices, each slice being a different person, complete with personality and history, all simultaneously. It was difficult to remember who I actually was for a while. Here is
my report (the first part... I went on to take DOC the next day).
Those are the ones I've tried that have stood out to me.