The JossIsBoss Game: (All characters created by the marvelous Joss Whedon)

**Mild spoiler alerts**

Name: Malcolm Reynolds
Played by: Nathan Fillion
Show: Firefly, Serenity
Job Description: Captain of a smuggling transport
Pros: Distrusting, cynical
Cons: Honorable, Doesn't work well with others

Name: Buffy Summers
Played By: Sarah Michelle Gellar
Show: Buffy the Vampire Slayer
Job Description: Vampire Slayer (Wasn't this one obvious guys?)
Pros: Capable of slaughtering demons, vampires, and other types of undead.
Cons: Only fights with wooden steaks.

Name: Dr. Horrible
Played By: Neil Patrick Harris
Show: Dr. Horrible's Sing Along Blog (And coming soon sequel!)
Job Description: Wannabe evil mastermind
Pros: Diabolical Genius, comedic flavor, much akin to the playing style of LanGadin
Cons: Distracted by love interest in Penny, very likely would have to sing much of his press

Name: River Tam
Played By: Summer Glau
Show: Firefly, Serenity
Job Description: Genius driven insane by genetic experiments to turn her into a psychic/assassin.
Pros: She's a freaking psychic
Cons: Would probably NMR every other turn due to insanity.

Name: Jayne Cobb
Played By: Adam Baldwin
Show: Firefly, Serenity
Job Description: Mercenary
Pros: No qualms about stabbing people
Cons: Doesn't lie well.

Name: Angel
Played By: David Boreanaz
Show: Angel, Buffy the Vampire Slayer
Job Description: Evil Vampire turned Good turned Private Investigator
Pros: Can't be killed except by a wooden stake, holy water or sunlight.
Cons: Can't go outside...

Name: Echo
Played By: Eliza Dushku
Show: Dollhouse
Job Description: Terrorist-activist who gets caught and turned into a programmable person.
Pros: Can simultaneously access any of thirty some odd personalities.
Cons: Struggles from a lack of identity

Who would win?
Jayne Cobb. The guys is a mercenary... I don't feel like writing anymore. :-P