// top of script

new RandomMSG[][] =
{
    "Come to this great stunt server! IP: ip_here",
    "Visit the server forums here: forum_site.com",
    "other ip's here",
    "other forum addresses here"
};

// ongamemodeinit

SetTimer("SendMSG", 60000, true); // sends every minute

// bottom of script

forward SendMSG();
public SendMSG()
{
    new randMSG = random(sizeof(RandomMSG)); //calculates the size of RandomMSG (which is 3)
    SendClientMessageToAll(-1, RandomMSG[randMSG]); // Replace the "color" with your defined color.
    return 1;
}