How about a drunk Irish guy with Leprechaun? Irish are pretty safe to make fun of, or they really don’t seem to care if you do, they will probably just beat the crap out of you if they get offended, which is rare.
Tub of Guts suit. What’s funnier than a fat person, right? I guess if you can dress as a skeleton then corpulence should be fine.
Jesus is about the only religious figure left that’s safe for ridicule (but not for all eternity). He’s the most tolerant of all the deities, and he died for your sins, so why not tempt fate and your eternal soul with a little blasphemous masquerading. Plus, it might be helpful to keep those demoniacs bound while you trick or treat.
In light of what’s appropriate or not for Halloween, we try to dress ourselves and children in costumes that won’t offend. Well, at least most of the population that don’t get offended. You know, like Fat Irish Christians.