I LOVED LOVED LOVED 6-apb when it was first released, the dirty brown TCP smelling powder was easily the most euphoric substance Ive ever taken. Subsequent batches, light tan powder lacked the euphoria of the first batch.
aMT and MXE gave me the most profound experience, losing my sense of reality with visuals so real I thought I would never come down. This was at stupid high doses of both.
Mephedrone was and is one of my favourites, highly euphoric and a sexual edge that's close to vaping MDPV (well nothing comes close to the hornyness of perve powder)
Ive experimented with lots of RC's over the years, I think the RC honeymoon is over now, bans in China, America and the UK has dampened the search for novel new substances