Yes, most.
The Bible records a medium in the Old Testament that King Saul used to contact Samuel. God wasn't answering King Saul's prayers because of Saul's sin. So Saul went to this medium to see if he could contact Samuel and find out what the problem was.
Samuel shows up and the medium lets out a scream. Leading many of us to speculate that this was the first time that the medium had ever really contacted the dead. And what Saul gets for his trouble is that Samuel rebukes him for using a medium.
In the New Testament in a certain town there is a woman who is possessed of a spirit that can tell the future. The town makes their money off of this woman. Paul visits the town preaching and the woman follows him around yelling in a loud voice for people listen to him that he will tell them about the Messiah. Apparently she must have done it in a mocking or disruptive way. Because Paul initially ignored her, but eventually Paul ordered the spirit out of her. When the town realized they had just lost their livelihood they tried to stone Paul and he had to make a quick exit.
Jesus and his disciples also cast demons (fallen angels) out of a few people. This wasn't merely illness. Jesus carries on a conversation with a group of demons in one person named Legion and casts them into a horde of pigs which promptly committed suicide by running over a cliff.
So the Bible records at least one medium that really did contact the dead and several accounts of demon possession.
On a personal note, once in Baton Rouge, I was woken up at 2AM by a guy trying to help a naked woman on my apartment's front lawn. The woman was writhing around like crazy and after calling for an ambulance, the guy came out and took the woman by the hand and ordered in the name of Jesus for Satan to come out of her about three times. Interestingly, the woman calmed down immediately after that. She didn't get up. She was still lying there, but much calmer. When the paramedics arrived she said she had taken several drugs and was off her medication. So I don't know whether it was just drugs or drugs and demon possession. But I did think her calming down in response to this guys impromptu exorcism was very curious.
The bible confirms that there are, in fact, spirits, that they can, in fact, be contacted for good purposes, and that, therefore, mediums may very well be doing a legitimate useful business.
Thanks for all the helpful information. Where would we be without alert spiritists such as yourself?
I'll alert the National Science Foundation of this incontrovertable evidence for the existence of spiritual possession.