Well so far back ache has been my most annoying. I have a slightly curved spine anyway so I used to get a bit of back pain but since being pregnant it's been terrible and getting worse.
My strangest is that I see things when I wake up which aren't there. They stay there for ages and don't go when I blink or look away and look back. I thought I was going mad but my doc thinks it's just caused by pregnancy.
As for unexpected, I think the fact that my moods calmed down. I had terrible PMT and was constantly getting in fights with OH. We were worried pregnancy hormones may make me even worse but I'm much better.