you should use local vars instead of global and add a flood pro to it as well.

on *:TEXT:!8ball *:#:{
  if (!$($+(%,8ballflood),2)) {
    set -u4 $+(%,8ballflood) on
    var %@ = No!|Yes|Maybe|Of course|Are you crazy?!?!|How should I know?|What are you smoking?|No way in hell!|Only on the weekends|Hahahaha, you make me laugh! 
    msg # 10 $gettok(%@,$r(1,10),124) 
  }
}