One who opposes and seeks to avoid violence and discord, typically in the context of playing video games. The name refers to the "Care Bears" plush teddy bears and cartoons. Matt won't play those shoot 'em up games with you—he's a total carebear.
carebear
n. a nice person who is against violence and disputes. (Especially in the domain of computer games. From the name of a set of lovable children’s characters.) These carebears don’t want us to play the really good games!