Killer whales have shown occasional tendencies to target people. Admittedly, most are captive so are a bit screwed up. There was that one in February
http://news.bbc.co.uk/1/hi/world/americas/8535618.stm there is another really spooky one on YouTube where a guest volunteer gets to ride on the orca which then refused to let her go and holds her with its mouth. Trainers intervene and she's released pretty shaken up (understandably) - this clip is still available but you've got to log in to see it (got to be >18years)
Here's a list of killers which kill
http://en.wikipedia.org/wiki/Orca_attacks_on_humansThe most interesting one (in my opinion) was the hunting of an Antarctic survey scientist by a group of killers which attempted to create a bow wave and flush him off an iceflow as they do seals. The attempt failed and scientist escaped! Sorry no reference for this one.
I've seen Orcas in the wild and up close in Vancouver Aquarium and they actually appear to me to look pretty nasty with their small little red eyes and massive size. Hits all my primeval fear buttons - I don't like big things in the water with me!