During the introductions, I gave my own favorite one. Kazumi Kato from Order of the Stick. Eight-months-pregnant, attacked by ninja who knock out her husband, she drinks a magic potion (she is, after all, a D&D character) and leaps to the attack:
"I'm a goddamn baby-making, life-taking MACHINE! Why should I care how many people I have to kill? I can just make MORE in my TUMMY!"Cordelia Vorkosigan came up, quickly; I hit on the advantages of authority and guns, which help mothers be kick-ass without the upper-body strength.
And I pointed out an obvious reason for childless female protagonists: because the unencumbered character is simplest. If the family relationship are not an integral part of the story, aesthetically, it's best to leave them out. Which means for characters of both sexes not only no children, but no spouse, no siblings, and no parents. Because if they are not integral to the story, they are unaesthetic clutter.
One audience member commented that while he would not have described himself as encumbered after his son's birth, on hearing it, it's very apt; so much of his life is focused on his son; he works, but it's to support his family. Discussing on how the importance of children to fathers is underplayed.
How Kick-Ass Moms are often rescuing their children, which helps eliminate two issues: who's looking after the children, and (the less frequently but more serious problem) why is she endangering her child? How an orphan hero prevents a Kick-Ass Mom from coming to his rescue; even Kick-Ass Mom usually is excused from duty by being dead. (Though if you read just about any variant of Cinderella but Perrault's, she's not helped by a fairy godmother; she's helped by her mother's ghost, which is embodied in the tree on her grave.)
Bad mothers as kick-ass -- they technically fall under the description even if they neglect their children.