The answer seems to depend on the writer and the circumstance. I'd probably buy into Cap, Superman, Beta Ray Bill (since it's fait accompli), and Odin.  All I feel confident about is that it has little to do with physical strength so I'm glad nobody has suggested the Hulk despite his having lifted Mjolnir numerous times.  Each time deserves an asterisk... sometimes the enchantment had been removed, sometimes it was a dream, sometimes he was really only holding Thor's arm / hand which was actually holding the hammer, sometimes he only thought he had picked it up but it was actually lifted because Thor had summoned it back to himself (something that also happened to Hercules).

Then there's that time Iron Man was carrying it in outer space

Vision lifted it all too easily (and with no explanation) in an Avengers movie.

Marc

Odin

Thor

Beta Ray Bill

Steve Rogers

I can buy Superman and even Wonder Woman. They have been established as up there as far as pretty good people.

I do like the idea that it really only works for moments of need per Busiek in the Avengers-JLA crossover. Steve Rogers is not going to be able to pick it up to hang a shelf.

If you guys have been keeping up with recent storylines:  Hydra Cap ("Stevil") was permitted to lift the hammer in FCBD Secret Empire ...this is probably the most controversial lifting IMO.

Also Jason Aaron's Thor storyline suggests that there is a sentient intelligence that is also in the mix here.

The panels Rick Senger posted above with the Hulk destroying Thor's hammer... If it was a dream sequence, does that really count as an example?

The Red Hulk (ugh) wielded Mjolnir against Thor in space, citing zero gravity as the reason he was able to. I find that absurd. If anything, Mjolnir should act like an anchor in zero gravity. You hang on to it, but you're going nowhere. 

People sometimes cling to the word "lift" when referencing the hammer and think there's a loophole if it's floating in space. I think the opposite.