IMHO, DXM is a waste at anything below the third plateau - and that's if you like weird dissociation with a lot of side effects.
I've never gotten anything from Salvia, but I'm not ready to write it off as worthless. It's in the "wouldn't pay for with my own money" category, but it's not something I'd never do again.
Methcathinone is iffy. For me, it was only a substandard stimulant which only gave me extra energy but no real high, plus the day after was fucking awful. Reduced to a gibbering sketchcase awful.
Ephedra - a horrid, horrid choice of stimulant. I knew a girl who'd eat those GNC ephedra capsules like they were candy, and I still cringe when I think of this.
DXM aside, I've never been too into the "let's get high off things from the grocery store" idea. I did have a roommate who ate dramamine for recreational purposes, but this was the same guy who was under the impression he could cultivate ergot fungus to synth his own acid, as long as he kept the soggy loaf of rye bread in my guitar case.