K + acid: deeply philosophical and introspective. generally amazing. if K is darkness and acid is light, then mixing them must obviously be expected to have nice results, right? that's what i thought, being a karbon-thugling at the time, and it was all good.
K + shrooms: similar to K + acid. however, i tried recovering from a bad trip with it, and it didn't work.
K + alcohol: not a good combination technically. makes you drunker. alcohol and K are both NMDA antagonists, and the NMDA antagonism of alcohol is responsible for the less pleasant effects, like the feeling of falling through space and the room spinning around you.
K + crystal: BAD. BAD. psychotic. schizophrenic. nasty. dirty. not a good combination. mixing two good substances does not necessarily ensure a good mix.
K + weed: i don't like weed cause it makes me extremely paranoid, but oh well. smoking weed even hours after doing K drastically increased hallucinations and synaesthesia.
K + DXM: perhaps not recommended, but good. very good. very real, vivid hallucinations with a plot and much significance. (the "in-flight movie") this caused me to witness the end of the universe to decent trance music while sitting in a dark, silent room.
K + painkillers: increases the effect of the painkillers, and happens to prevent tolerance. the amount of K required is small.