Dwarves

They appear more than you think! Dwarves all wear horned helmets and are experts at metal-smithing. Their trademark phrase is "Lali-ho!" (which really should be "Rally-ho!". Those crazy Japanese phoenetics...).

1: You have to talk to Nerrick the Dwarf in "Dwarf Cave" (original name, eh?) in order to obtain TNT to blow a hole into the main sea. Later on, you can get the Dwarves to forge you a strong sword using Adamant.
3: Dwarves are in need of your help, and you must quest to retrieve their horn(s). Again, their town is called "Dwarf Cave". The Viking job class looks practically identical to a dwarf.
4: There's an entire kingdom of Dwarves found in the underground world. Giott's daughter, Luca, is the only visibly female dwarf in the entire series.
5: There is a "kingdom" of dwarves consisting of about half a dozen citizens.
9: The Dwarves just look like little people with Jay Leno chins. Their calling phrase is finally translated correctly - "Rally-ho!"