Mean things that kids do to each other

Verbal abuse is underestimated. It's the most common and one of the most effective ways the kids screw each other.

From personal experience, I can add

• While in a pool physically keeping you underwater.
• Cheating in Monopoly and finding excuses so that you can't (Such as: Refusing to leave prison in the end game. I couldn't because I got there last and someone had to be out there.)
• Always allying against you in games where it's possible (like risk), using plausible excuses for doing so. (You're too strong!)
• Making you the target of every single joke, and generally being against you at all times.

All these come from family members. From other kids I never experienced anything other than verbal abuse. (Which can potentially be more than enough.)

Forgive the late post, but this just occurred to me: throwing shoes over power lines. It happened all the time when I was a kid. Bullies steal a kid's shoes, tie the laces together and throw them until they get hung on power lines. Then the poor victim has to walk home barefoot and face mom's wrath for loosing his shoes. For what I understand, it is a particularly popular mode of abusing poor kids, as they get much more grief from loosing shoes than anyone else.

• Pushing you down a tall hill.
• Stealing your shoes and throwing them in a lake.
• Throwing you into a pull even though you can't swim.
• Canning gravel in your eyes.
• Not letting you play on the school play equipment.
• Taking you toys and breaking them.
• Taking your books.

School life can be hell for a kid.

Take into mind that the abuse that hurts the most is the kind that completely removes any sense of control. Have the bully make the bullied child absolutely at his mercy. Tidal Wave mentioned throwing things into a body of water. Perhaps the bully could dangle something important to the child over a murky lake and the bullied child cannot swim. He'll beg and plead to get his MacGuffin back, but the bully would taunt him, making him beg repeatedly. This would constitute "getting a rise out of him" which is the ultimate goal of a bully, and in the end, the bully can simply drop the MacGuffin in the water. Threatening with any such mean spirited prank will work.

Another way to induce helpless is to have the bully insult something that the bullied child cannot change, such as clothes, speech (accent, lisp, etc.), the way he walks, the way he looks, family income, religion.

Have the bully slap, trip or kick the kid just after a teacher walks by so that the kid cannot retaliate without getting in trouble. Have the kid be framed quite often by the bully, it'll drive him crazy and ruin his image. The teacher will never believe him and thusly take away his sense of control in the situation.

Simple pushing also can be terrible. When no authority figure is standing by, it does not make sense to slap, kick or trip the kid. So, the bully and his friends will push the kid between them, being pushed is simple and reduces his ability to retaliate.