#define CMD_VAR "cmdVar"
#define CMD_DELAY (60)

forward myTimer();

/* Use it under OnFilterScriptInit() if you want to use it as a filterscript or under OnGameModeInit() if you want to use it as a gamemode. */
SetTimer("myTimer", 1000, true);

public myTimer()
{
  foreach(Player, u)
  {
    if(GetPVarInt(u, CMD_VAR) > 0) SetPVarInt(u, CMD_VAR, GetPVarInt(u, CMD_VAR) - 1);
  }
  return true;
}

command(kill, playerid, params[])
{
  #pragma unused params
  if(GetPVarInt(playerid, CMD_VAR) == 0)
  {
    SetPlayerHealth(playerid, 0);
    SetPVarInt(playerid, CMD_VAR, CMD_DELAY);
  }
  else
  {
    new
        arr[64];
    format(arr, sizeof(arr), "SERVER: You'll have to wait %i more seconds to use this command.", GetPVarInt(playerid, CMD_VAR));
    SendClientMessage(playerid, 0xFFFFFFFF, arr);
  }
  return true;
}