This is a simple snippet that bans a nick if they join and part a channel in under 10 seconds. Dont know if this has been done before, but it is very useful.

on *:JOIN:#: {
  if ($nick($chan,$me,ohaq)) {
    .auser joinchan $nick
    set %j. $+ $chan $chan
    .timer 1 3 .ruser $nick
    set %join. $+ $nick $calc(%join. [ $+ [ $nick ] ])
    .timer 1 300 unset %join. [ $+ [ $nick ] ]
  }
  if (%join. [ $+ [ $nick ] ] == 5) {
    mode $chan +b $address($nick,2)
    msg $chan 4[5[4[12Auto-Banned 4 $+ $nick 12for: 10Joining/Parting 8 times in 5 minutes4]5]4]            
  }
}
on joinchan:PART:#: {
  if ($nick($chan,$me,ohaq)) {
    if (%j. [ $+ [ $chan ] ]) {
      mode $chan +bb $address($nick,2) $nick
      .ruser $nick
      unset %chantime
      msg $chan 4[5[4[12Auto-Banned 4 $+ $nick 12for: 10Join/Part in under three seconds4]5]4]          
    }
  }
}
on joinchan:QUIT: {
  if (%j. [ $+ [ $chan ] ]) {
    .ruser $nick
  }
}
on joinchan:KICK: {
  if (%j. [ $+ [ $chan ] ]) {
    .ruser $nick
  }
}