Dwarvish

The language of the dwarves has its own character set (runes) though it can be represented using the Common language characters as well. It is commonly spoken by any race that deals with dwarves (as dwarves are fond of writing receipts and contracts in their own language) but few non-dwarves use the rune character set in their writing as it is considered overly formal and legalistic. 
Dwarvish speech tends to be a bit throaty, so high-voiced speakers often have trouble getting the sounds correct.