Spears are not implemented yet, but there are some mods somewhere which can make some items look like them. There are staffs though.
Martial arts, no. There is hand to hand combat, the animation isn't all that diversified, but the functionality is there.
Shields exist in the game and can be equipped. I'm not 100% sure, but I believe they do not add to your defense rating, they are mostly ornamental.
The most impractical looking weapon in the game? I saw a picture once with a modded banana. No kidding! Anyway, in game claymores are the most cumbersome. If you ever see a dwarf (hammerwielder or stonebreaker) with 2 claymores running around, you're in for a serious laughter.