A rogue with mask, full wf invasion gear, and fishing trinkets comes out at 47.5625 - so that would be the highest "normal" ilvl for rogues.
Theres a few unique cases. There are a few people who were able to get their hands on big items before they were patched - see that warrior that there was a complaint about a few months back who had a ilvl 300 something neck. Probably a few other grandfathered pieces that I don't really know about.
You could also use the chains as weapons. Would be terrible damage for a rogue, but if all you're caring about is ilvl it goes up to 55.81
A druid with similar gear and 2x chains would get to 51.6875 and actually still be useful. A clothie with inferno robe, an invasion wand and link of chain would be 48.375 and have the wand boost. Switching to 2x chains would get to 52.5 and still be mostly useful, but definitely not worth the loss of the wand.
Now as to who has that gear...idk. My rogue is up there, but I haven't bothered with the fishing trinkets (over AGM/insignia) and have a few half-warforged pieces - so definitely not the highest.
EDIT: I missed the ilvl 27 cloak...but not redoing calcs for the 25->27 diff.