David Darwinson is one of the U.S. Marshals that can be selected under the "Marshals" category in the Outfitter. The Marshals category was unlocked without restrictions by Rockstar Games on October 1, 2010 on all systems.
"You'll be pissin' outta your ass when I'm done with you!"
"I'd stick my iron up your asshole if I could!"
"Buzzards will like ya'."
"How much your momma charge, the no good that spawned you?"
"I shat out a prettier thing than you this mornin'."
"A face wound's about the only thing that'll improve your looks."
"You're just another dumb bastard that got killed in the West."