This question is pretty self-explanatory. I like the character of Beta Ray Bill, but haven't gotten into much of his comics. How does his hammer work? Is it like Mjolnir, as in based on worthiness, or is it based on something else?
The "worthiness" rule with Mjolnir was placed on it by Odin when Thor was being punished on Earth to learn humility. He assumed that only Thor would ever be "worthy" enough to use it.
However, Beta Ray Bill was deemed worthy to use Thor's hammer, based on the quest he was on. (There's always some debate on whether the hammer itself "chooses", or if it's based on some parameter set in the spell)
After some fighting (it's a comic book, there's always fighting), Odin declared that he'd earned his own hammer, which works only for him.
It also has the power to return Bill to his original pre-cyborg form, if he so wishes.