They're hard to get ahold of, but I kinda like the 'compression/decompression' chamber method (described by Tom Clancy in one of his novels).
Nothin' like a good dose of the 'bends' to extract info - the pain is constant until you're re-compressed. Done properly, it doesn't leave a mark!.........FRegards
Pretty sure that was "Without Remorse" which was brilliant but a little sick.