Gunslassin. "Falling to your death isn't just for old people, plenty of window washers and electricians go that way too."
Well neither of them is exceptionally sassy, but whenever CG says something mean she apologizes, so Gunslinger I guess.
Ford Prefect. "Hey, you sass that hoopy Ford Prefect? There's a frood who really knows where his towel is." (Sass: know, be aware of, meet, have sex with; hoopy: really together guy; frood: really amazingly together guy.)" ? Douglas Adams, The Hitchhiker's Guide to the Galaxy
I don't play assassin, but does she even have voice lines, besides her horribly faked giggles? She's the opposite of sassy.