Vylbrand and quests originating in Vylbrand are a great source for Eorzean swearing and cussing in general. Starter MSQs, Rogues' Guild, Marauders' Guild to a lesser extent, etc.
Unofficially....
*cracks knuckles and flexes fingers*
"Ruttin' hells."
"Gods damn you!"
"Gods-damned pissant."
"Shite...."
"Tuco piss."
"Son of a coeurl!"
"Thal's Balls."
"Matron's teats!"
"Oschon's Staff."
"Sweet Menphina...."
"Twelve Above."
...and countless variations and so on and so forth.
Unofficially....
*cracks knuckles and flexes fingers*
"Ruttin' hells."
"Gods damn you!"
"Gods-damned pissant."
"Shite...."
"Tuco piss."
"Son of a coeurl!"
"Thal's Balls."
"Matron's teats!"
"Oschon's Staff."
"Sweet Menphina...."
"Twelve Above."
...and countless variations and so on and so forth.