Corny but great.
Captain America proves that he is worthy enough to lift Thor’s hammer, from Thor #390 (April 1988) by Tom DeFalco, Ron Frenz, and Brett Breeding:
This was from a period in Captain America’s history when he had resigned his usual superhero identity and became “The Captain,” independent of any government agency, in case you were wondering what was up with the costume.
I tend to have a soft spot for stories where characters (like Beta Ray Bill or Superman) find themselves worthy enough to lift Thor’s hammer Mjolnir, which normally only Thor himself is able to do.
Yes, I know that’s a weird thing for which to have a soft spot. What can I tell you?
EDIT: Please see Comics Should Be Good’s Top Five Non-Thor Mjolnir Wielders article for more information.