Actually quite a bit.
They steal like goblins AND kobolds, and they can drink like a mountain gnome to mess up your fort.
They are considered a detestable vermin, so certain dwarves will get unhappy thoughts from them.
They have a syndrome attack of Orc Drool, which spatters onto people from orcish bites, which cause nasuea and blood vomiting (mostly put them in to cause more unhappy thoughts, I made them to cause more phychological damage than physical).
Bites also suck a small amount of blood out, though I don't think it makes to much of a difference.
They like fighting and will almost constantly rage, and can trance.
They can convert other races into more orcs, but usually don't cause they have their own civ(mostly put in for kidnapped children, for when world continuation is put in next release)
They have an orc roar ability that work simailar to a mummy's curse, but not as powerful and will wear off eventually.
Oh, and undead Orcs are hostile to everything, even their own body parts
They also have a "snatch" attack that works similarily to latching on when biting, only with the hands.
Hmm, can't think of anything else at the moment, but yeah.