We could do without Wolverine, methinks. That guy's overexposed as it is. No need to have him show up in roleplays too. Besides, Marvel is just too silly for me.
If you think you could pull it off you could use Dark Horse Comics Hellboy; a demon with a love of cats, chocolate bars & cigars, who carries his adoptive father's rosary beads within always despite being a demon, who uses big ass gun and interacts with supernatural world on a daily basis.
Or
If you could pull out Rorschach from the Watchmen Universe, after all Mr. Manhattan did vanish him at the end so who is to say he can't reappear in Nexus City. Axe Cop and Rorschach would not get along, one is a lawman and the other is a vigilante that is willing to kill his prey if not cripple them.
Or
You could pluck either a Villain or Hero Character from the DC Universe.