The Hammer is technically weightless otherwise Thor being on the helicarrier or a plane would make it fall out of the sky. That being said it has a spell on it that only someone who is worthy of its power may wield it.
To clarify, Mjolnir has been enchanted by Odin so that NO ONE can wield it who is not worthy of its power, regardless of how strong they may be. That said, however, it would be POSSIBLE for Hulk to wield it IF he managed to prove "worthy".
The Hulk could wield it only if his rage made him more powerful than Odin. Given that he physically overpowered Onslaught when it at least had the power of a Celestial, it is theoretically possible, but we don't know.