Originally posted by Rhapsody:

If it's a single dvergr, backstab them with Skoll and Hati or any other powerful secondary attack. If it's a bunch of dvergr, especially in a tower, you can snipe them with crossbow for nearly guaranteed insta-kills.

Originally posted by knighttemplar1960:

They are weak to fire. If you snipe them with fire arrows before they see you a no star greydwarf will go down in one hit. Except for the shaman and the brute they are also afraid of fire and will run from you if you are holding a lit torch.

I don't see any fire weakness listed on the wiki, I'd stick to crossbow.

It wasn't clear from the OP if he meant grey dwarves or Dverger. Since experienced players would have an idea I assumed he was completey new and was talking about grey dwarves since that's the majority of the dwarf questions on the forums and also the reason I specifically mention grey dwarves in my reply.