I agree that mushrooms taste great. I never understood the hatred for that taste.
The best tasting drugs to me, however, are opiates. They taste like shit when you aren't adjusted to them, but after a positive relationship with them is formed, they taste delicious. Oxycodone tastes the best, followed by heroin. I can't remember how oxymorphone tastes, but I remember enjoying it. There are some similarities in taste that let me know that I'm tasting an opioid, and my mind and body adjust accordingly, allowing me to feel better 15-30 minutes before the shit even kicks in. Best taste in the world.
The only exception would be buprenorphine. For some reason, this one tastes like shit no matter how used to it I am. I'm not just talking about Suboxone with all the nasty ass sweeteners, but Subutex as well. I can chew up six percocets with all that APAP right there and not gag, but if I allow that bupe to escape the pit of my tongue and get onto any taste receptors, I feel like I'm about to throw up, even though I've been doing it twice a day for three or four years now.
Oh, and coke also tastes delicious. I don't particularly like the feeling, nor do I hate it, but it is hard to deny that it tastes good. And anything involving high grade weed also tastes good.