If we're going beyond just 2 drug combos, I remember quite liking the oxycodone + (IV) morphine + diazepam + cannabis combo.
But who wouldn't enjoy that?
Methadone + Xanax is a doozy. I used to call that the "knockout special" (approx. 50 mgs of methadone syrup + 1-2 mgs of alprazolam). It'll cure your insomnia quick!
^ I really like methadone, too. A pleasant surprise in the drug world that I only recently discovered. It's strong as fuck (IMO), especially when you decide to get really stupid with it and throw some tranquilizers into the mix. Never used it for maintenance purposes but it was good for getting high purposes...
I'd never, ever want to be addicted/dependent on it, though