AHK - SendDelay()

This function will have a script send "key" only once every "delay" milliseconds.

SendDelay(key,delay) {
   Global
   If (lastSent_%key% = "" || lastSent_%key% < A_TickCount - delay)
   {
      Send %key%
      lastSent_%key% := A_TickCount
      Return 1
   }
   Return 0
}

For example, the following script will send the "a" key once every 1.5 seconds.

Loop
   SendDelay("a",1500)

For a better example, see the post AHK - World of Warcraft - Shaman ES/SS spam