//sscanf+zcmd /announce by Seven_of_Nine
COMMAND:announce(playerid,params[]) {
    new
        poster[40],
        mess[128];
    if(PlayerInfo[playerid][pAdminLevel] >= 3) {
        if(sscanf(params,"s",mess))
            return SendClientMessage(playerid,red,"USAGE: /announce [message]");
        if(!isnull(mess)) {
            new text[128];
            GetPlayerName(playerid,poster,sizeof(poster));
            format(text,sizeof(text),"[Announce] | Administrator \"%s\" has announced his message. (%s)",poster,mess);
            SendClientMessageToAll(COLOR_LIGHTBLUE,text);
            GameTextForAll(mess,5000,3);
        } else {
            return SendClientMessage(playerid,red,"USAGE: /announce [message], and all players will see this message on-screen.");
        }
    } else {
        return SendClientMessage(playerid,red,"Only lvl3 admins can use this command. Looking for a way to announce? Try /message!");
    }
    return 1;
}

COMMAND:command(playerid, params[])
{
    new string[128], pName[MAX_PLAYER_NAME];
    if(sscanf(params,"s[128]", params)) return SendClientMessage(playerid, -1, "Usage: /command <text>");
    GetPlayerName(playerid,pName,sizeof(pName));
    format(string, sizeof string, "Adminstrator %s: %s", pName params);
    SendClientMessageToAll(-1, string);
    return 1;
}