In my first year of junior high (7th grade), a few months after getting beaten up - I was getting my lunch money out of my locker, and two 9th grade boys reached around me to steal my money. I grabbed each arm with my hands, dug in my not-too-long, but still long-enough nails, and starting spinning. I spun around like a top and when I let go of each arm, the boy attached to it hit a pole and fell to the ground. These were two tall, big 15-year-olds, and I was a very short, chubby 12-year-old. The two boys ran to a teacher and told her I had beaten them up. She looked at them. She looked at me. She laughed for a really long time and told the boys to get lost. They never bothered me again. In fact, nobody bothered me again. Word had gotten around.
I learned that if you confront one bully, all the others will back off - permanently.
Great story. And you're absolutely right.
My brother had a similar one. He was a small boy as a teen, and worse, our father was a principal at this high school, so he got picked on a lot and also endured some physical abuse, though nothing quite as serious as all the beatings described in this thread (as far as I know), always by the same group of boys. Of course, he was a victim purely on the fact that he was small, quiet, and was the principal's son, but then again, when did bullies ever need a reason to bully someone?
One day, he encountered one of those boys, who happened to be alone. Strangely, that boy didn't bully him when he wasn't with his gang. This happened a few times until one day the boy decided he could probably get away with bullying my brother without his gang, too, and so he tried. Since he was alone, though, my brother, though smaller than him, decided it was time to defend himself, and grabbed the kid and shoved him in the wall. After a punch or two in the belly, he told the boy to leave him the hell alone. My brother said he vividly recalls the kid's shocked surprise; I guess he never expected the smaller kid to fight back. He wasn't bullied since. He considers himself lucky to have been able to fight back, since most bullies always stick together as group.
As for me... I can't say I've ever really been bullied. Picked on a lot, yes, was very unpopular, but verbal assaults never made any impression on me since I had endured far worse from my two older brothers growing up

and the taunts I gave back were usually sharper than they'd expect. The only times I was physically bullied was in elementary school; once, a boy kept teasing me, so I teased him back, and apparently he didn't like that so he threw a snowball to my face. Only that snowball hurt like hell, because it was actually a ball of frozen ice covered in a bit of snow. When my brother (the same as earlier -- keep in mind he's 8 years older than me

) asked about the bruise, he told me that if that kid ever tried to hurt me again, to tell him right away and he'd beat the crap out of him. Luckily (for me and for that kid), it never happened haha.
And the other time was by this insane and violent girl who bullied -everyone-. She was a very troubled child, come to think of it, probably endured a lot of abuse at home.... She was stronger than your average boy and picked fights with everyone. She once elbowed a boy (not a small one, too, an athletic kid, at least for elementary school) so bad in the back that they had to call an ambulance. I knew to avoid her, but somehow I encountered her once, not sure what the circumstances were. All she did was lift me by the collar and stick me against the wall (my legs were dangling, I was a very short girl in elementary school but she was freakishly strong for a 10 year old girl or so), uttering threats, then she thankfully released me and I never encountered her again.
I'm not sure if I could really call this girl a bully, since I don't think (to my vague recollection) she'd single out someone as a long-term target. I actually kind of feel sorry for her, unlike most bullies like the kids who bullied my brother and those described in this thread.