Definitely heroin, although I haven't tried many others mainly due to how expensive they are, and all the ones I have tried with the exception of butyrfentanyl, morphine, and kratom are because I got them prescribed back when I had insurance so I didn't even have to pay for them. To clarify, the only other opioids I've ever tried are codeine, hydrocodone, and tramadol so there's a lot of opioids that I have yet to try, who knows, maybe someday I'll try an opioid that I like better than heroin, but until then heroin is my most favorite.